THE BRAINS OF EARTH

By Jack Vance

Scanned by BW-SciFi

Copyright ©, 1966, by Ace Books, Inc.

All Rights Reserved

Printed in U.S.A.

I
 Ixax at the best of times was a dreary planet. Winds roared through the jagged black mountains, propelling jets of rain and sleet which, rather than softening the landscape, tended to wash what soil existed into the ocean. Vegetation was scant: a few drab forests of brittle dendrons; wax-grass and tube-wort bunching out of crevices; lichens in sullen splotches of red, purple, blue and green. The ocean however, supported extensive beds of kelp and algae; these, with a fairly abundant catalogue of marine animalculae, conducted the greater part of the planet's photo-synthetic process.
In spite of, or because of, the challenge of the environment, the original amphibian animal, a type of ganoid batrachian, evolved into an intelligent andromorph. Assisted by an intuitive awareness of mathematical justness and harmony, with a visual apparatus that presented the world in tactile three-dimensional style rather than as a polychrome set of two-dimensional surfaces, the Xaxans were almost preordained to build a technical civilization. Four hundred years after their advent into space they discovered the nopal—apparently through the workings of sheer chance—and so involved themselves in the most terrible war of their history.
The war, lasting over a century, devastated the already barren planet. Scum crusted the oceans; the few sparse pockets of soil were poisoned by yellowish-white powder sifting out of the sky. Ixax had never been a populous world; the handful of cities now were rubble: heaps of black stone, liver-brown tile, chalk-white shards of fused talc, wads of rotting organic stuff, a chaos which outraged the Xaxan compulsion for mathematical exactness and nicety. The survivors, both Chitumih and Tauptu (so to transcribe the clicks and rattlings of the Xaxan communicative system), dwelt in underground fortresses. Distinguished by Tauptu awareness and Chitumih denial of the nopal, they nourished toward each other an emotion akin to but a dozen times more intense than Earthly hate.
After the first hundred years of war the tide of battle ran in favor of the Tauptu. The Chitumih were driven to their stronghold under the Northern Mountains; the Tauptu battle-teams inched forward, blasting the surface defense-ports one by one, dispatching atomic moles against the mile-deep citadel.
The Chitumih, although aware of defeat, resisted with a fervor corresponding to their more-than-hate for the Tauptu. The rumble of approaching moles sounded ever louder; the outlying mole-traps collapsed, then the inner-ring of diversion-tunnels. Looping up from a burrow ten miles deep, an enormous mole broke into the dynamo chamber, destroying the very core of Chitumih resistance. The corridors went pitch-dark; the Chitumih tumbled forth blindly, prepared to fight with hands and stones. Moles gnawed at the rock; the tunnels reverberated with grinding sound. A gap appeared, followed by a roaring metal snout. The walls broke wide apart; there was a blast of anaesthetic gas, and the war was over.
The Tauptu climbed down across the broken rock, search-lights glowing from their heads. The able-bodied among the Chitumih were pinioned and sent to the surface; the crushed and mangled were killed where they lay.
War-Master Khb Tachx returned to Mia, the ancient capitol, flying low through a hissing rain-storm across a dingy sea, over a foreland pocked with great craters in the shape of earth-colored star-bursts, over a range of black mountains, and the charred rubble of Mia lay before him.
There was a single whole building in evidence, a long squat box of gray rock-melt, newly erected.

Khb Tachx landed his air-car, and ignoring the rain, walked toward the entrance of the building. Fifty or sixty Chitumih huddling in a pen slowly turned their heads, sensing him with the perceptors which fulfilled the function of eyes. Khb Tachx accepted the impact of their hate with no more attention than he gave the rain. As he approached the building a frantic rattle of torment sounded from within, and again Khb Tachx paid no heed. The Chitumih were more affected. They shrank back as if the pain were their own, and in clenched dull vibrations reviled Khb Tachx, defying him to do his worst.
Khb Tachx strode into the building, dropped to a level a half-mile below the surface, proceeded to the chamber reserved for his use. Here he removed his helmet, his leather cloak, wiped the rain from his gray face. Divesting himself of his other garments he scrubbed himself with a stiff-bristled brush, removing dead tissue and minute surface scales from his skin.
An orderly grated his finger-tips across the door. "You are awaited."
"I will come at once."
With a passionless economy of motion he dressed in fresh garments, an apron, boots, a long cape smooth as a beetle-shell. It so happened that these garments were uniformly black, although this was a matter of indifference to the Xaxans who differentiated surfaces by texture rather than color. Khb Tachx took up his helmet, a casque of striated metal, crowned by a medallion symbolizing the word tauptu—"purged". Six spikes rose from the keel, three corresponding to the inch-high knuckles of bone along his cranial crest, the remaining three denoting his rank. After a moment's reflection Khb Tachx detached the medallion, then pulled the helmet down over his bare gray scalp.
He left his chamber, walked deliberately along the corridor to a door of fused quartz, which slid soundlessly aside at his approach. He entered a perfectly circular room with vitreous walls and a high paraboloid dome. Insofar as the Xaxans derived pleasure from the contemplation of inanimate objects, they enjoyed the serene simplicity of these particular conformations. At a round table of polished basalt sat four men, each wearing a six-spike helmet. They immediately noticed the absence of the medallion from Khb Tachx's helmet, and derived the import he meant to convey: that with the collapse of the Great Northern Fortress the need for distinction between Tauptu and Chitumih had ended. These five governed the Tauptu as a loose committee, without clear division of responsibility except in two regards: War-Master Khb Tachx directed military strategy; Pttdu Apiptix commanded those few ships remaining to the space-fleet.
Khb Tachx seated himself, and described the collapse of the Chitumih stronghold. His fellows apprehended him impassively, showing neither joy nor excitement, for they felt none.
Pttdu Apiptix dourly summed up the new circumstances. "The nopal are as before. We have won only a local victory."
"Nevertheless, a victory," Khb Tachx remarked.
A third Xaxan countered what he considered an extreme of pessimism. "We have destroyed the Chitumih; they have not destroyed us. We started with nothing, they everything: still we have won."
"Immaterial," responded Pttdu Apiptix. "We have been unable to prepare for what must come next. Our weapons against the nopal are makeshift; they harass us almost at will."
"The past is past," Khb Tachx declared. "The short step has been taken; now we will take the long one. The war must be carried to Nopalgarth."
The five sat in contemplation. The idea had occurred many times to all of them, and many times they had drawn back from the implications.
A fourth Xaxan remarked abruptly, "We have been bled white. We can wage no more war."
"Others now will bleed," Khb Tachx responded. "We will infect Nopalgarth as the nopal infected Ixax, and do no more than direct the struggle."
The fourth Xaxan reflected. "Is this a practical strategy? A Xaxan risks his life if he so much as shows himself on Nopalgarth."
"Agents must act for us. We must employ someone not instantly recognizable as an enemy—a man of another planet."
"In this connection," Pttdu Apiptix remarked, "there is a first and obvious choice ..."

II
 A voice which quavered from fright or excitement  —the girl at the ARPA switchboard in Washington could not decide which—asked to speak to "someone in charge." The girl inquired the caller's business, explaining that ARPA consisted of many departments and divisions.
"It's a secret matter," said the voice. "I gotta talk to one of the higher-ups, somebody connected with the top science projects."
A nut, decided the girl, and started to switch the call to the public relations office. At this moment Paul Burke, an assistant director of research, walked through the foyer. Burke, loose-limbed, tall, with a reassuringly nondescript appearance, was thirty seven, once-married, once-divorced. Most women found Burke attractive; the switchboard operator, no exception, seized the opportunity to attract his attention. She sang out, "Mr. Burke, won't you speak to this man?"
"Which man?" asked Burke.
"I don't know. He's quite excited. He wants to talk to someone in authority."
"May I ask your position, Mr. Burke?" The voice evoked an instant image in Burke's mind: an elderly man, earnest and self-important, hopping from one foot to the other in excitement.
"I'm an assistant director of research," said Burke.
"Does that mean you're a scientist?" the voice asked cautiously. "This is business that I can't take up with underlings."
"More or less. What's your problem?"
"Mr. Burke, you'd never believe me if I told you over the phone." The voice quavered. "I can't really believe it myself."
Burke felt a trace of interest. The man's voice communicated its excitement, aroused uneasy prickles at the nape of Burke's neck. Nevertheless, an instinct, a hunch, an intuition told him that he wanted nothing to do with this urgent old man.
"I've got to see you, Mr. Burke—you or one of the scientists. One of the top scientists." The man's voice faded, then strengthened as if he had turned his head away from the mouth-piece as he spoke.
"If you could explain your problem," said Burke cautiously, "I might be able to help you."
"No," said the man. "You'd tell me I was crazy. You've got to come out here. I promise you you'll see something you've never imagined in your wildest dreams."
"That's going pretty far," said Burke. "Can't you give me some idea what it's all about?"
"You'd think I was crazy. And maybe I am." The man laughed with unnecessary fervor. "I'd like to think so."
"What's your name?"
"Are you coming out to see me?"
"I'll send someone out."
"That won't do. You'll send the police, and then—there'll —be—trouble!" He almost whispered these last words.
Burke spoke aside to the operator, "Get a tracer on this call." Into the phone he said, "Are you in trouble yourself? Anyone threatening you?"
"No, no, Mr. Burke! Nothing like that! Now tell me the truth: Can you come out to see me right now? I got to know!"
"Not unless you give me a better reason than you have."
The man took a deep breath. "Okay. Listen then. And don't say I didn't warn you. I—" The line went dead.
Burke looked at the telephone in mingled disgust and relief. He turned to the operator. "Any luck?"
"I didn't have time, Mr. Burke. He hung up too soon." Burke shrugged. "Crack-pot, probably . . . But still . . ." He turned away, neck still tingling eerily. He went to his office, where presently he was joined by Dr. Ralph Tarbert, a mathematician and physicist dividing his time between Brookhaven and ARPA. Tarbert, in his middle fifties, was a handsome lean-faced man, nervously muscular, with a shock of electric white hair of which he was very proud. In contrast to Burke's rather rumpled tweed jackets and flannel slacks, Tarbert wore elegant and conservative suits of dark blue or gray. He not only admitted but boasted of intellectual snobbery, and affected a cynicism which Burke sometimes found frivolous enough to be irritating.
The unfinished telephone call still occupied Burke's mind. He described the conversation to Tarbert who, as Burke had expected, dismissed the incident with an airy wave of the hand.
"The man was scared," mused Burke, "no question about that."
"The devil looked up from the bottom of his beer mug."
"He sounded stone-sober. You know, Ralph, I've got a hunch about this thing. I wish I'd gone to see the man."
"Take a tranquilizer," suggested Tarbert. "Now, let's talk about this electron-ejection thing . . ."
Shortly after noon a messenger brought a small package to Burke's office. Burke signed the book, examined the package. His name and address had been printed with a ballpoint pen; there was also an inscription: OPEN IN ABSOLUTE PRIVACY.
Burke ripped open the parcel. Inside he found a cardboard box, containing a dollar-size disk of metal, which he shook out into his hand. The disk seemed at the same time light and heavy; massive but weightless. With a soft exclamation Burke opened his hand. The disk floated in midair. Slowly, gently, it began to rise.
Burke stared, reached. "What the devil," he muttered. "No gravity?"
The telephone rang. The voice asked anxiously, "Did you get the package?"
"Just this minute," said Burke.
"Will you come to see me now?"
Burke took a deep breath. "What's your name?"
"You'll come alone?"
"Yes," said Burke.

III
sam gibbons was a widower, two years retired from a prosperous used-car business in Buellton, Virginia, sixty-five miles from Washington. With his two sons at college, he lived alone in a big brick house two miles from town, on the crest of a hill.
Burke met him at the gate—a pompous man of sixty, with a pear-shaped body, an amiable pink face now mottled and trembling. He verified that Burke was alone, made sure that Burke was both a recognized scientist—"up on all that space and cosmic ray stuff"—and in a position of authority.
"Don't get me wrong," said Gibbons nervously. "It's gotta be this way. You'll see why in a few minutes. Thank God I'm out of it." He blew out his cheeks, looked up toward his house.
"What goes on?" asked Burke. "What's all this about?"
"You'll know soon enough," said Gibbons hoarsely. Burke saw that he was staggering with fatigue, that his eyes were red-rimmed. "I've got to bring you to the house. That's all I do. From then on it's up to you."
Burke looked up the driveway toward the house. "What's up to me?"
Gibbons patted him nervously on the shoulder. "It's all right; you'll just be—"
"I'm not moving until I know who's there," said Burke.
Gibbons glanced furtively over his shoulder. "It's a man from another planet," he blurted through wet lips. "Mars maybe; I don't know for sure. He made me telephone somebody he could talk to, and I got hold of you."
Burke stared toward the front of the house. Behind a window, veiled by curtains, he glimpsed a tall square-shouldered shape. It never occurred to him to doubt Gibbons. He laughed uncertainly. "This is rather a shock."
"You're telling me," said Gibbons.
Burke's knees were stiff and weak; he felt an enormous reluctance to move. In a hollow voice he asked, "How do you know he's from another planet?"
"He told me," said Gibbons. "I believed him. Wait till you see him yourself."
Burke drew a deep breath. "Very well. Let's go. Does he speak English?"
Gibbons smiled in feeble amusement. "Out of a box. He has a box on his stomach and the box talks."
They approached the house. Gibbons pushed the door open, motioned Burke to enter. Burke stepped forward, stopped short in the hall.
The creature who waited was a man, but he had arrived at his estate by a different route from that traveled by Burke's forebears. He stood four inches taller than Burke, with a skin rough and gray as elephant hide. His head was narrow and long, his eyes blank and blind-looking, like cabochons of beer-colored quartz. A bony crest rose from his scalp, studded with three bony knobs. Striking down from his brow the crest became a nose, thin as a scimitar. The chest was deep and narrow, the arms and legs corded and ropy with sinew.
Burke's faculties, numbed by the sheer drama of the situation, slowly returned. Studying the man, he sensed a harsh fierce intelligence, and became uneasily conscious of dislike and distrust—feelings which he strove to suppress. It was inevitable, he thought, that creatures of different planets must find each other uncomfortable and strange. Trying to compensate he spoke with a heartiness that rang false even to his own ears. "My name is Paul Burke. I understand that you know our language."

"We have studied your planet for many years." The voice came in discrete and distinct words from an apparatus hanging over the alien's chest: a muffled unnatural voice accompanied by hisses, buzzings, clicks and rattles, produced by vibrating plates along the creature's thorax. A translation machine, thought Burke, which presumably retranslated English words into the clicks and rattles of the stranger's speech. "We have wished to visit you before but it is dangerous for us."
" 'Dangerous'?" Burke was puzzled. "I can't understand why; we're not barbarians. Which is your home planet?"
"It is far away from your solar system. I do not know your astronomy. I can not name it. We call our planet Ixax. I am Pttdu Apiptix." The box seemed to find difficulty with l's and r's, pronouncing them with a rasping and rattling of the glottal mechanism. "You are one of your world's scientists?"
"I am a physicist and mathematician," said Burke, "although now I hold an administrative position."
"Good." Pttdu Apiptix held up his hand, turned the palm toward Sam Gibbons who stood nervously at the back of the room. The small squat instrument he held chattered, shivering the air as a hammer-blow splinters ice. Gibbons croaked, fell to the floor in a strange round heap, as if all his bones had vanished.
Burke sucked in his breath, aghast. "Here, here!" he stammered. "What are you doing?"
"This man must not talk to others," said Apiptix. "My mission is important."
"Your mission be damned!" roared Burke. "You've violated our laws! This isn't—"
Pttdu Apiptix cut him short. "Killing is sometimes a necessity. You must alter your way of thinking, because I plan that you help me. If you refuse, I will kill you and find another."
Burke's voice refused to make itself heard. At last he said hoarsely, "What do you want me to do?"
"We are going to Ixax. There you will know."
Burke remonstrated gently, as if addressing a maniac. "I can't possibly go to your planet. I have my job to look after. I suggest that you come with me to Washington—" He stopped short, embarrassed by the other's sardonic patience.
"I care nothing for your convenience, or your work," said Apiptix.
On the verge of hysterical anger Burke trembled, leaned forward. Pttdu Apiptix displayed his weapon. "Do not be influenced by your emotional urges." He twisted his face in a wincing grimace—the only change of facial expression
Burke had noticed. "Come with me, if you wish to live." He backed away, toward the rear of the house.
Burke followed on stiff legs. They went out a rear door into the back yard, where Gibbons had built himself a swimming pool and a tiled barbecue area.
"We will wait here," said Apiptix. He stood motionless, watching Burke with the blank stolidity of an insect. Five minutes passed. Burke could not speak for a weakness of rage and apprehension. A dozen times he leaned forward on the brink of plunging at the Xaxan and taking his chances; a dozen times he saw the instrument in the harsh gray hand and drew back.
Out of the sky dropped a blunt metal cylinder the size of a large automobile. A section fell open. "Enter," said Apiptix.
For the last time Burke weighed his chances. They were non-existent. He stumbled into the car. Apiptix followed. The section closed. There was an instant sensation of swift motion.
Burke spoke, holding his voice steady with great effort. "Where are you taking me?"
"To Ixax."
"What for?"

"So that you will learn what is expected of you. I understand your anger. I realize that you are not pleased. Nevertheless you must grasp the idea that your life is changed." Apiptix put away his weapon. "It is useless for you to—"
Burke could not control his rage. He flung himself at the Xaxan, who held him off with a rigid arm. From somewhere came a mind-cracking blaze of purple light, and Burke lost consciousness.

IV
burke awoke in an unfamiliar place, in a dark chamber smelling of damp rock. He could see nothing. Under him was what seemed to be a resilient mat; exploring with his fingers he found a hard cold floor a few inches below.
He rose on his elbow. There was no sound to be heard: an absolute silence.
Burke felt his face, tested the length of his beard. There was bristle at least a quarter-inch long. A week had passed.
Someone was approaching. How did he know? There had been no sound; only an oppressive sense of evil, almost as palpable as a physical stench.
The walls glowed with sudden luminosity, revealing a long narrow chamber, with a graceful vaulted ceiling. Burke raised himself on the pad, arms trembling, legs and knees flaccid.
Pttdu Apiptix, or someone closely resembling him, appeared in the doorway. Burke, tight in the chest from tension, giddy from hunger, staggered to his feet.
"Where am I?" His voice rasped huskily in his throat.
"We are on Ixax," spoke the box on Apiptix's chest.
Burke could think of nothing to say; in any event his throat had choked up.
"Come," said the Xaxan.
"No." Burke's knees slackened from under him; he sank back on the mat.
Pttdu Apiptix disappeared into the corridor. Presently he returned with two other Xaxans who rolled a metal cabinet. They seized Burke, thrust a tube down his throat, pumped warm liquid into his stomach. Then, without ceremony, they withdrew the tube, departed.
Apiptix stood silently, and several minutes passed. Burke lay supine, watching from under his eyelids. Pttdu Apiptix was weirdly magnificent, demoniac and murderous though he might be. A glossy black shell like the carapace of a beetle hung down his back; on his head he wore a striated metal helmet with six baleful spikes raising from the crest. Burke shivered weakly and closed his eyes, feeling unpleasantly weak and helpless in the presence of so much evil strength.
Another five minutes passed, while the vitality slowly seeped back through Burke's body. He stirred, opened his eyes, said fretfully, "I suppose now you'll tell me why you've brought me here."
"When you are ready," said Pttdu Apiptix, "we will go to the surface. You will learn what is required of you."
"What you require and what you'll get are two different things," growled Burke. Feigning lassitude, he leaned back on the mat.
Pttdu Apiptix turned, departed, and Burke cursed himself for his own perversity: what did he achieve lying down here in the dark? Nothing but boredom and uncertainty.
An hour later Pttdu Apiptix returned. "Are you ready?"
Wordlessly Burke raised himself to his feet, followed the black-shrouded figure along the passage, into an elevator. They stood close together, and Burke wondered at the contraction of his flesh. The Xaxan was representative of the universal type man: why the revulsion? Because of the Xaxan's ruthlessness? Reason enough, thought Burke; still…
The Xaxan spoke, interrupting Burke's train of thought. "Perhaps you ask yourself why we live below the surface?"
"I'm asking myself about many things."
"A war drove us underground—a war such as your planet has never known."
"This war is still going on?"
"On Ixax the war is ended; we have purged the Chitumih. We can walk on the surface again."
Emotion? Burke wondered. Was intelligence without emotion conceivable? A Xaxan's emotions were not necessarily commensurable with his own, of course; still they must share certain viewpoints, certain aspects of intelligent existence, such as the urge to survive, satisfaction in achievement, curiosity and puzzlement...
The elevator halted. The Xaxan stepped out, set off down the corridor. Burke followed reluctantly, sorting through a dozen wild and impractical stratagems. Somehow, in some way, he must exert himself. Pttdu Apiptix planned nothing good for him; action of any sort was preferable to this meek compliance. He must find a weapon—fight, run away, escape, hide—something, anything!
Apiptix wheeled around, gestured abruptly. "Come," intoned his voice-box. Burke advanced slowly. Act! He chuckled sardonically, relaxing. Act, how? So far they had offered him no harm, still ... A sound brought him up short: a terrible staccato rattle. Burke needed no help to understand; the language of pain was universal.
Burke's knees wobbled. He put his hand to the wall. The rattle broke, vibrated, buzzed weakly away.
The Xaxan eyed him dispassionately. "Come," spoke the voice-box.
"What was that?" whispered Burke.
"You will see."
"I won't come any farther."
"Come, or you will be carried."
Burke hesitated. The Xaxan moved toward him; Burke lurched forward in anger.
A metal door rolled aside; a chill sour wind sang through the gap. They emerged upon the dreariest landscape of Burke's experience. Mountains like crocodile teeth rimmed the horizon; the sky was wadded with black and gray clouds, from which hung funereal smears of rain. The plain below was crusted with ruins. Corroded girders poked at the sky like dry insect legs; walls had fallen into tumbles of black brick and liver-brown tile; the sections still standing were blotched with fungus in sullen colors. In all the sad scene there was nothing fresh, nothing alive, no sense of change or better things to come; only decay and futility. Burke could not restrain a pang of compassion for the Xaxans. No matter what their transgressions . . . He turned back to the single erect building, that from which he and Pttdu Apiptix, stared at the dark shapes within the pen. Men? Xaxans?
The box on the chest of Pttdu Apiptix answered his unspoken query. "Those are the remnant of the Chitumih. There are no more. Only the Tauptu remain."
Burke walked slowly toward the pathetic huddle, pressing into the bitter gusts of wind. He came to the mesh, looked through. The Chitumih returned his inspection, seeming to feel him with their eyes, rather than look at him. They were a miserable tattered group, the skin rough and taut over their framework of bone. In racial type they appeared identical to the Tauptu, but here the similarity ended. Even in the shame and squalor of the pen their spirit burnt clear. The ancient tale, thought Burke: barbarism triumphant over civilization. He glared at Apiptix, whom he saw to be a vicious creature, barren of decency. Sudden fury surprised and overwhelmed Burke. He became light-headed and staggered forward, swinging his fists. The Chitumih buzzed soft encouragement, but to no avail. A pair of nearby Tauptu stepped forward. Burke was seized, pulled away from the pen, pressed against the wall of the building, held until he ceased struggling and went limp and panting.
Apiptix spoke through his voice-box, as if Burke's futile assault had never occurred. "Those are the Chitumih; they are few and soon will be eliminated."
Through the rock-melt walls came another terrified vibration.
"Torture the Chitumih—and let the others listen?"
"Nothing is done without reason. Come, you shall see."
"I've seen enough." Burke peered wildly around the horizon. He saw no succor and no place to run, only wet ruins, black mountains, rain, corrosion, crumble. . . . 

Apiptix made a sign; the two Tauptu led Burke back into the building. Burke resisted. He kicked, hung limp, thrashed his body back and forth to no avail; the Tauptu carried him without effort along a short wide corridor, into a chamber flooded with a green-white glare. Burke stood panting, the two Tauptu still beside him. Again he tried to struggle loose, but their fingers were like tongs.
"If you are able to control your aggressive impulses," spoke the emotionless voice-box, "you will be released."
Burke choked off a bitter flow of words. Struggle was useless, undignified. He straightened himself, nodded curtly. The Tauptu stood back.
Burke looked around the room. Half-hidden behind a bank of what appeared to be electrical circuitry he saw a flat frame of shining metal bars. Against the wall four Xaxans stood in fetters; Burke recognized them for Chitumih through some quality he could not define: an inner sense which assured him that the Chitumih were decent, kind, courageous, his natural allies against the Tauptu. . . . Apiptix came forward carrying what appeared to be a pair of lenseless spectacles.
"At the moment there is much that you do not understand," Apiptix told him. "Conditions are different from those on Earth."
Thank God for the difference, thought Burke.
Apiptix continued. "Here on Ixax there are two sorts of people: the Tauptu and the Chitumih. They are distinguished by the nopal."
" 'Nopal'? What is the nopal?"
"You are about to learn. First, I wish to make an experiment, to test what might be called your psionic sensitivity." He displayed the lenseless spectacles. "These instruments are constructed of a strange material, a substance unknown to you. Perhaps you would like to look through them."
A pulse of aversion for all things Tauptu jerked him back. "No."
Apiptix extended the spectacles. He seemed to be grimacing in humor, though no muscle of his corded gray face quivered. "I must insist."
With an effort Burke controlled his fury, snatched the spectacles, fitted them to his eyes.
There appeared to be no visual change, no refractive effect whatever.
"Examine the Chitumih," said Apiptix. "The lenses add—let us say—a new dimension to your vision."
Burke examined the Chitumih. He stared, bent his head forward. For an instant he saw—what? What was it he had seen? He could not remember. He looked again, but the lenses blurred his vision. The Chitumih wavered; there was a black fuzzy blot, like a caterpillar, across the top half of their bodies. Peculiar! He looked at Pttdu Apiptix. He blinked in surprise. Here was the black blur as before—or something else? What was it? Incomprehensible! It served as background to the head of Apiptix—something complex and indefinable, something vastly menacing. He heard a strange sound, a grating guttural growl—"Gher, gher." Where did it come from? He pulled off the glasses, looked wildly about him. The sound ceased.
Apiptix clicked and buzzed; the voice-box asked, "What did you see?"
Burke tried to remember exactly what he had seen. "Nothing I could identify," he said finally, but his mind had gone blank. Strange . . . And it came to him to wonder, half-wildly, what on earth's going on? And then he remembered; I'm not on Earth. . ..
He asked aloud, "What was I supposed to see?"
The Xaxan's reply was drowned in a staccato rattling yammer of pain. Burke clasped his hands to his head, and, beset by a strange drunken vertigo, swayed and tottered. The Chitumih were also affected; they drooped and two sank to their knees.
"What are you doing?" cried Burke hoarsely. "Why have you brought me here?" He could not look toward the machinery at the end of the chamber.
"For a very necessary reason. Come. You shall see."
"No!" Burke plunged toward the door. He was caught and held. "I don't want to see any more."
"You must."
The Xaxans swung Burke around, led him struggling across the room. Willy-nilly he was forced to look at the mechanism. A man lay spread-eagled face-down on the metal grill. Two cusps of complicated construction embraced his head; tight metal sleeves confined his arms, legs, torso. A film of cloth fragile as fog, transparent as cellophane, half floated above his head and upper shoulders. To Burke's astonishment the victim was no Chitumih. He wore the garments of a Tauptu; on a table nearby rested a helmet similar to that of Apiptix, displaying four prongs. A fantastic paradox! Burke watched in bewilderment as the process —punishment, torment, exhibition, whatever it might be— continued.
Two Tauptu approached the grill. Their hands were cased in white gloves. They kneaded the cloth which shrouded the victim's head. The arms and legs squirmed. From the cusps issued a sudden silent vibration of blue light—a discharge of some sort of energy. The victim rattled and Burke struggled dizzily against the grip of the Xaxans. Once more the blue discharge; again the jerky mechanical reflex, like the kicking of a frog's leg to electricity. The Chitumih by the wall clicked miserably; the Tauptu stood stern and inexorable.
The torturers kneaded, worked, pulled. Another burst of blue light, another despairing rattle; the Tauptu on the grill lay limp. The torturer removed the transparent bag, carried it gingerly away. Two other Tauptu removed the unconscious man, laid him unceremoniously on the floor. Then they seized one of the Chitumih, flung him on the grill. His arms and legs were pinioned; he lay frothing and straining in terror. The impalpable cloth was brought in, floating weightlessly in the air, arranged over the Chitumih's head and shoulders.
The torture began. . . . Ten minutes later the Chitumih, head lolling, was carried to the side of the room.
Apiptix handed the quivering Burke the spectacles. "Observe the purged Chitumih. What do you see?"
Burke looked. "Nothing. There is nothing."
"Now look here. Quickly!"
Burke turned his head to look into a mirror. Something stiff and pompous reared above his head. Great bulbous eyes stared from beside his neck. Just a flicker of a vision, then he saw nothing. The mirror blurred. Burke tore off the glasses. The mirror was clear, revealing only his ashen face. "What was that?" he whispered. "I saw something . . ."
"That was the nopal," said Apiptix. "You surprised it." He took the spectacles. Two men seized Burke, carried him fighting and kicking to the grill. The sleeves rolled over his arms and legs; he was immobilized. The cloth was arranged over his head. He caught a final glimpse of the malignant, infinitely hateful face of Pttdu Apiptix; then a shuddering shock of pain pounded the nerves of his back-bone.
Burke bit his lips, strained to move his head. Another blast of blue light, another spasm of pain, as if the torturers were rapping his raw nerves with hammers. The muscles of his throat distended. He could hear nothing, he was unaware of his own screaming.
The flare vanished; there was only a kneading of white-gloved hands, a sucking burning sensation as of a scab being pulled from a sore. Burke tried to beat his head against the bars of the grill, moaned to think of his agony here on this evil black world. . . . An excruciating shatter of blue energy; a pull, a rip, as if the spine had been broken out of his body; a deep insane rage, and then he lost consciousness.

V
burke felt rather light-headed, as if he had been stimulated by some euphoric drug. He lay on a low resilient mat, in a chamber similar to that which he had occupied before.
He thought of his last conscious moments, of the torment, and sat up full of wild recollection. The doorway was open, unguarded. Burke stared, visions of escape racing through his head. He started to rise, then heard footsteps. The opportunity was lost. He returned to his former position.
Pttdu Apiptix appeared in the doorway, stolid and massive as an iron statue. He stood watching Burke. After a moment Burke rose slowly to his feet, prepared for almost anything.
Pttdu Apiptix came forward. Burke watched him in wary hostility. And yet—was this really Pttdu Apiptix? It seemed the same man; he wore the six-pronged helmet, and carried the voice-box slung over his chest. He was Pttdu Apiptix and he was not—for his semblance had altered. He no longer seemed evil.
The voice-box said, "Come with me; you will eat and I will explain certain things to you."
Burke could find no words; it seemed as if his captor's entire personality had changed.
"You are puzzled?" Apiptix asked. "For good reason. Come."
Burke followed in a daze of perplexity to a large room furnished as a refectory. Apiptix motioned him to a seat, went to a dispenser, returned with bowls of broth and cakes of a dark substance like compressed raisins. Yesterday the man had tortured him, thought Burke; today he acts the part of a host. Burke examined the broth. He had few food prejudices, but the comestibles of a strange world, prepared from unknown substances, did not encourage his appetite.
"Our food is synthetic," said Apiptix. "We cannot indulge in natural foods. You will not be poisoned; our metabolic processes are similar."
Burke ignored his qualms and dipped into the broth. It was bland, neither pleasant nor otherwise. He ate in silence, watching Apiptix from the corner of his eye. No sudden— possibly illusory—change of manner could compensate for the cold-blooded facts: murder, kidnapping, torture.
Apiptix finished quickly, eating without nicety or grace, then sat with his eyes feeling at Burke, as if in saturnine reflection. Burke glared back sullenly. He thought of an enlarged photograph of a wasp's head he had once seen. The eyes, great bulbs, fibrous, faceted, stolid, were similar to the eyes of the Xaxans.
"Naturally enough," Apiptix remarked, "you are puzzled and resentful. You understand nothing of what has been happening. You wonder why I appear differently today than yesterday. Is this not true?"
Burke admitted that such was the case.
"The difference is not in me; it is in you. Look." He pointed up into the air. "Look up there."
Burke searched the ceiling. Spots swam before his eyes; he tried to blink them away. He saw nothing, and looked to Apiptix for explanation.
Apiptix asked, "What did you see?"
"Nothing."
"Look again." He pointed. "There."
Burke looked, peering through the streaks and blotches in front of his eyes. Today they were unusually troublesome. "I can't see . . ." He paused. He seemed to sense staring owlish eyes. When he tried to find them they swam and melted into the floating spots.

"Keep looking," said Apiptix. "Your mind has no training. Presently the things will become clear."
"What things?" asked Burke in perplexity.
"The nopal."
"There's nothing whatever."
"Do you not see phantoms, impalpable shapes? It is easier, far easier for an Earthman to see than a Xaxan."
"I see spots before my eyes. That's all."
"Look carefully at the spots. That particular spot, for example."
Wondering how Pttdu Apiptix could be aware of spots before someone else's eyes, Burke studied the air. The blotch seemed to focus, to concentrate: ominous orbs stared at him; he sensed a shifting flutter of color. He exclaimed, "What is this? Hypnotism?"
"It is the nopal. It infests Ixax in spite of our efforts. You are finished eating? Come, once again you shall observe the Chitumih yet unpurged."
They walked outside, into the black downpour of rain which seemed to fall almost continuously. Pools gleamed among the ruins, pallid as mercury; the jagged mountains behind could not be seen.
Pttdu Apiptix, ignoring the rain, stalked to the Chitumih enclosure. Only two dozen prisoners remained; they glared through the dripping mesh with eyes of hate, and now the hate included Burke.
"The last of the Chitumih," said Apiptix. "Look at them again."
Burke peered through the mesh. The air over the Chitumih was blurred. There were— He uttered a startled exclamation. The blur resolved. It now appeared that each of the Chitumih carried a strange and terrible rider, clinging to his neck and scalp by means of a gelatinous flap. A proud bank of bristles reared up behind each of the Chitumih heads, sprouting from a wad of dark fuzz the size and shape of a football. Two globes hung between the human shoulders and ears, apparently serving the same function as eyes. If eyes they were, they turned on Burke with the same hate and defiance which showed on the faces of the Chitumih.
Burke found his voice. "What are they?" he asked huskily. "The nopal?"
"They are the nopal. Parasites, abominations." He made a gesture around the sky. "You will see many others. They hover over us, hungry, anxious to settle. We are anxious to rid our planet of the things."
Burke searched the sky. The hovering nopal, if any, were inconspicuous in the rain. There—he thought to see one of the things, floating like a jellyfish in water. It was small and undeveloped; the spines were sparse, the bulbs which might or might not be eyes appeared no larger than lemons. Burke blinked, rubbed his forehead. The nopal disappeared, the sky was empty of all but dour wind, torn clouds. "Are they material?"
"They exist; therefore they are material. Is this not a universal truth? If you ask what kind of material, I cannot tell you. War has occupied us a hundred years, we have had no opportunity to learn."
Hunching his neck against the rain Burke turned back to look at the imprisoned Chitumih. He had considered them noble in their defiance; now they seemed rather brutish. Odd. And the Tauptu, who had aroused his detestation ... He considered Pttdu Apiptix who had kidnapped him and disrupted his life, who had murdered Sam Gibbons. Hardly a likeable person—still Burke's revulsion had dwindled, and a certain grudging admiration mingled with his dislike. The Tauptu were harsh and hard, but they were men of uncompromising resolution.
A sudden idea occurred to Burke, and he eyed Apiptix suspiciously. Had he been victim to a marvelous and subtle job of brain-washing, which converted hate into respect, fostered illusions of non-material parasites? Not a convincing idea under the circumstances—but what could be more bizarre than the nopal itself?

He turned back to the Chitumih, and the nopal glared as before. He found it hard to think clearly; nevertheless certain matters had become clarified. "The nopal don't concentrate on Xaxans alone?" he asked of Pttdu Apiptix.
"By no means."
"One of them had settled on me?"
"Yes."
"And you put me on that grill to purge this nopal?"
"Yes."
Burke mulled the information over, with the cold rain trickling down his back. The toneless voice-box said, "Your irrational hates and sudden intuitions are less frequent, you will notice. Before we could deal with you, it was necessary that you be purged."
Burke forbore to inquire the nature of the dealings. He looked up to find the small nopal floating near at hand, the eye-orbs glistening down at him. Five feet? Ten feet? Fifty feet? He could not determine the distance; it seemed vague, almost subjective. He asked, "Why don't the nopal settle on me again?"
Apiptix made his stiff odd grimace. "They will do so. Then once more you must be purged. One month, more or less, they keep their distance. Perhaps they are afraid; perhaps the brain can hold them away this long. It is a mystery. But sooner or later they come down; then we are Chitumih and must be purged."
The nopal exercised a morbid fascination; Burke found it hard to wrench his eyes away. One of the things had been joined to him! He shivered, feeling a rather irrational gratitude to the Tauptu for purging him—even though they had brought him to Ixax in the first place.
"Come," said Apiptix. "You will learn what is required of you."
Wet and cold, feet squelching in his shoes, Burke followed Apiptix back into the refectory. He felt utterly miserable. Apiptix who took no heed of rain or wet, motioned Burke to a seat.
"I will tell you something of our history. A hundred and twenty years ago Ixax was a different world. Our civilization was comparable to yours, although in certain respects we were more advanced. We have long traveled space and your world has been known to us for several centuries.
"A hundred years ago a group of scientists—" He paused, peered quizzically at Burke. "The wetness disturbs you? You are cold?" Without waiting for reply he clicked and buzzed to an attendant, who brought a heavy blue glass mug of hot liquid.
Burke drank; the fluid was hot and bitter, evidently a stimulant. He presently felt more cheerful, even light-headed, while the water dripped from his clothes and ran in a puddle along the floor.
The voice-box spoke in a measured monotone, enunciating l's and r's with careful trills. "A hundred years ago certain of our scientists, investigating what you call psionic activity, discovered the nopal. In this fashion Maub Kiamkagx"—so the name came through the voice-box—"a man highly teletactile, was trapped in a faulty power modulating machine. For several hours energy played around him and into him. He was rescued, and the scientists resumed their tests, anxious to learn whether the experience had affected his abilities.
"Maub Kiamkagx had become the first Tauptu. When the scientists approached he looked at them in terror; the scientists likewise felt an illogical antagonism. They were puzzled and tried to locate the origin of their dislike, to no avail. Meanwhile Maub Kiamkagx was wrestling with his sensations. He apprehended the nopal, at first ascribing them to teletactility or even hallucination. Actually he was 'tauptu'—purged. He described the nopal to the scientists who were incredulous. 'Why haven't you noted these horrible things before?' they asked.

"Maub Kiamkagx formed the hypothesis which has driven us to victory over the Chitumih and their nopal: "The experience in the power-generator has killed the creature which preyed on me. This is my guess.'
"An experiment took place. A criminal was purged in a similar fashion. Maub Kiamkagx declared him clear of nopal. The scientists felt the same irrational hate for both men, but were impelled by their capacity for right-judging—" (an allusion to the peculiar Xaxan capacity for sensing mathematical and logical equivalence, which Burke failed to grasp)"—to doubt the hate, understanding its peculiar appropriateness if the statements of Maub Kiamkagx were accurate.
"Two of the scientists were purged. Maub Kiamkagx pronounced them 'tauptu.' The remaining scientists in the group underwent purging—and this was the original nucleus of the Tauptu.
"The war started soon. It was bitter and cruel. The Tauptu became a miserable band of fugitives, living in ice-caves, torturing themselves monthly with energy, purging such Chitumih that they were able to capture. Eventually the Tauptu began to win the war, and only a month ago the war ended. The last Chitumih waits outside to be purged.
"That is the story. We have won the war on this planet. We have eliminated Chitumih resistance, but the nopal remain; and once a month we must torment ourselves on the energy grill. It is intolerable, and we will never quit our war until the nopal are destroyed. So the war is not over for us, but has merely entered a new phase. The nopal are few on Ixax, but this is not their home. Their citadel is Nopalgarth; Nopalgarth is the pest-hole. This is where they thrive in untold multitudes. From Nopalgarth they flit to Ixax with the speed of thought, to drop upon our shoulders. You must go to Nopalgarth; you must inspire destruction of the nopal. This is the next stage of the war against the nopal, which someday we must win."
Burke was silent a moment. "Why can't you go to Nopalgarth yourself?"
"On Nopalgarth the Xaxans are conspicuous. Before we could achieve our aim we would be persecuted, killed or driven away."
"But why did you select me? What good can I do—even admitting that I agree to help you?"
"Because you will not be conspicuous. You can achieve more than we can."
Burke nodded dubiously. "The inhabitants of Nopalgarth are men like myself?"
"Yes. They are of a species identical to your own. This is not surprising, since Nopalgarth is our name for Earth."
Burke smiled skeptically. "You must be mistaken. There are no nopal on Earth."
The Xaxan performed his wry wincing grimace. "You have not been aware of the infestation."
A queasy apprehension rose in Burke's throat. "I can't see how this can be true."
"It is true."
"You mean that I had the nopal on Earth, before I came here?"
"You have had it all your life."

VI
burke sat looking into the turmoil of his own thoughts while the voice-box on the chest of Pttdu Apiptix droned relentlessly on.
"Earth is Nopalgarth. Nopal fill the air over your hospitals, rising from the dead, jostling about the new-born. From the moment you enter the world to the time you die, you carry your nopal."
"Surely we'd know," muttered Burke. "We'd have learned, just as you did . . ."
"We have a history thousands of years longer than yours. Only by accident did we find the nopal. ... It is enough to make us wonder what other matters take place beyond our knowing."
Burke sat glum and silent, feeling the rush of oncoming tragic events beyond his power to avert. A number of other Xaxans, perhaps eight or ten, filed into the refectory, sat in a line facing him. Burke looked along the line of blade-nosed faces; the blind-looking mud-colored eyes stared back over him—passing judgment, so Burke felt obscurely. "Why do you tell me this?" he asked abruptly. "Why did you bring me here?"
Pttdu Apiptix sat straighter, massive shoulders square, gaunt face harsh and still. "We have cleansed our world at great cost. The nopal find no haven here. For a single month we are free—then the nopal of Nopalgarth slip down upon us, and we must torture ourselves to be purged."
Burke considered. "And you wish us to clean Earth of the nopal."
"This is what you must do." Pttdu Apiptix said no more. He and his fellows sat back, judging Burke.
"It sounds like a big job," Burke said uneasily. "Too big for one man—or for one man's lifetime."
Pttdu Apiptix gave his head a terse jerk. "How can it be easy? We have purged Ixax—and in the process Ixax has been destroyed."
Burke, staring glumly into space, said nothing.
Pttdu Apiptix watched him a moment. "You wonder if the cure is not worse than the disease," came his words.
"Such a thought occurred to me."
"In a month the nopal will once more settle upon you. Will you allow it to remain?"
Burke remembered the purging process—anything but a pleasant experience. Suppose he did not purge himself when the nopal returned? Once secure upon his neck the nopal would be invisible—but Burke would know it to be there, the proud bush of spines spread like a peacock's tail, the orbs peering owlishly over his shoulders. Fibrils, penetrating his brain, would influence his emotions, derive nourishment from heaven knew what intimate source. . . . Burke drew a deep breath. "No, I won't allow it to remain."
"No more will we."
"But to purge Earth of the nopal—" Burke hesitated, dazed by the scope of the problem. He shook his head in frustration. "I don't see what can be done. . . . Many different kinds of people live on Earth: different nationalities, religions, races—billions of people who know nothing of the nopal, who don't want to know, who wouldn't believe me if I told them!"
"I understand this very well," Pttdu Apiptix replied. "The same situation existed on Ixax a hundred years ago. Only a million of us now survive, but we would fight the war again—or another war, if need be. If the Earth people do not cleanse their corruption, then we must do so."
The silence was heavy. When Burke spoke his voice rang dull, like a bell heard under water. "You threaten us with war."
"I threaten a war against the nopal."
"If the nopal are driven from Earth they will merely collect on another world."
"Then we will pursue them, until finally they are gone."
Burke shook his head fretfully. Somehow, in a manner he could not quite identify, the Xaxan's attitude seemed fanatic and irrational. But there was an enormous amount he failed to understand. Were the Xaxans imparting everything they knew? He said rather desperately, "I can't make so big a commitment; I've got to have more information!"
Pttdu Apiptix asked, "What do you wish to know?"
"A great deal more than you've told me. What are the nopal? What kind of stuff are they made of?"
"These matters are extraneous to the issue. Nevertheless I will try to satisfy you. The nopal are a life-form somehow related to conceptualizing—we know no more."
" 'Conceptualizing'?" Burke was puzzled. "Thought?"
The Xaxan hesitated, as if he too might be confused by the difficulties of semantic exactness. " 'Thought' means something different to us than to you. However, let us use the word 'thought' in your sense. The nopal travel through space faster than light, as fast as thought. Since we do not know the nature of thought, we are ignorant as to the nature of the nopal."
The other Xaxans observed Burke with stolid dispassion, standing like a row of antique stone statues.
"Do they reason? Are they intelligent?"
" 'Intelligent'?" Apiptix made a curt clicking sound which the voice-box failed to translate. "You use the word to mean the kind of thinking that you and your fellow men perform. 'Intelligence' is an Earth-human concept. The nopal do not think as you think. If you gave a nopal one of your so-called 'intelligence tests' its score would be very low, and you would view it with amusement. Nevertheless it is able to manipulate your brain much more easily than it can manipulate ours. The style of your thinking and the nature of your visual processes is quicker and more flexible than ours, and more susceptible to nopal suggestion. The nopal find fertile pasture among the brains of Earth. As to the intelligence of the nopal, it functions to augment the success of its existence. It realizes your capacity for horror and hides from view. It knows the Tauptu for its enemies and encourages hate in the Chitumih. It is crafty and fights for its life. It is not without initiative and resource. In the most general sense, it is intelligent."
Annoyed by what he interpreted as condescension, Burke said shortly, "Your ideas regarding 'intelligence' may or may not be logical; your ideas regarding the nopal seem cumbersome, and your purging methods absolutely primitive. Is it necessary to use torture?"
"We know no other way. Our energies have been engaged in warfare; we have had no time for research."
"Well—the system won't work on Earth."
"You must make it work!"
Burke laughed hollowly. "The first time I tried it I'd be thrown into jail."
"Then you must build an organization to prevent this, or to provide you with concealment."
Burke shook his head slowly. "You make it sound so simple. But I'm only one man; I wouldn't know where to start."
Apiptix shrugged, an almost Earth-type gesture. "You are one man, you must become two. The two must become four; the four, eight, and so on until all Earth is purged. This was the process we followed on Ixax. It has cleared Ixax of Chitumih, and so it is successful. Our population will restore itself, we will rebuild our cities. The war is no more than an instant in the history of our planet; so shall it be on Earth."
Burke was unconvinced. "If Earth is infested with nopal, it should be decontaminated—no argument there. But I don't want to start a panic, not even a general disturbance, let alone a war."
"No more did Maub Kiamkagx," intoned the voice-box of Pttdu Apiptix. "The war began only when the Chitumih discovered the Tauptu. The nopal urged them to hatred; they fought to annihilate the Tauptu. The Tauptu resisted, captured and purged Chitumih. There was war. Events may go the same way on Earth."
"I hope not," said Burke curtly.
"So long as the nopal of Nopalgarth are destroyed, and quickly, we will not be critical of your methods."
There was another period of silence. The Xaxans sat frozen. Burke rested his forehead wearily in his hands. Confound the nopal, confound the Xaxans, confound the entire complicated mess! But he was in it and there seemed no way to get out. And even though he could not find the Xaxans a likeable folk he was forced to admit the justice of their complaint. So: where was his choice? He had none. "I will do my best," he said.
Apiptix showed neither satisfaction nor surprise. He rose to his feet. "I will teach you what we know of the nopal. Come."
They returned through a damp corridor to the hall which Burke had labeled the 'denopalization chamber.' The machinery was in use. With a crawling stomach Burke watched as a female, struggling and gasping, was fixed to the grill. Burke's eyes—or was it another sense?—now saw the nopal clearly. It flinched in the glare of greenish light, spines swollen and askew, eye-bulbs pulsing, fuzzy thorax working helplessly.
Burke turned to Apiptix in disgust. "Can't you use an anaesthetic? Is it necessary to be so harsh?"
"You misunderstand the process," the Xaxan replied, and somehow the voice-box managed to convey an undertone of grim contempt. "The nopal is not troubled by the energy; it is weakened and dislodged by the turmoil of the brain— by the Chitumih's certainty of pain. The Chitumih are housed beside the chamber where they can hear the cries of their fellows. It is unpleasant—but it weakens the nopal. Perhaps in time you will find more effective techniques on Earth."
Burke muttered, "I hope so. I can't stand too much of this torture."
"You may be obliged to do so." The voice-box spoke with its usual tonelessness.
Burke tried to turn his back on the denopalization grid, but could not restrain fascinated glances. There was frantic rattling and palpitation of the female's thorax. The nopal clung desperately to the woman's scalp; finally it was wrenched loose and carried off in the loose near-transparent sack.
"What happens now?" Burke asked.
"The nopal finally becomes useful. Possibly you have wondered about the sack, you have asked yourself how it contains the impalpable nopal?"
Burke acknowledged as much.
"The substance of the sack is dead nopal. We know no more about it than that, for it does not respond to investigation. Heat, chemicals, electricity—nothing of our physical world affects it. The stuff exhibits neither mass nor inertia; it coheres to nothing but itself. However the nopal cannot penetrate a film of the dead nopal-stuff. When we dislodge a nopal from a Chitumih, we capture it and crush it thin. This is very easy, for the nopal crumbles at a touch— when the touch is transmitted through the nopal-stuff." He looked at the denopalizing machine and a wisp of nopal-cloth came floating over to him.
"How did you do that?" asked Burke.
"Telekinesis."
Burke felt no particular surprise; in the context of what he had learned the procedure seemed quite natural, quite ordinary. He thoughtfully examined the nopal-stuff. It seemed vaguely fibrous, like a cloth woven of spider-web. There were certain implications to the fact of this material, its easy response to telekinesis . . . Apiptix spoke, breaking into his train of thought.

"Nopal-cloth is the lens-material of the spectacles through which you looked yesterday. We do not know why Chitumih can sometimes sense a nopal when light is filtered through a film of the nopal's dead brother. We have speculated, but the laws which govern nopal-matter are not those of our own space. Perhaps this will be the spearhead of your attack on the nopal of Nopalgarth: the discovery and systematization of a new science. You have facilities and thousands of trained minds on Earth. On Ixax are only tired warriors."
Burke thought wistfully of his old life, of the secure niche he could never reoccupy. He thought of his friends, of Dr. Ralph Tarbert, of Margaret—vital, cheerful Margaret Haven. He saw their faces and imagined their nopal, riding like pompous Old Men of the Sea. The picture was ludicrous and tragic. He could well understand the fanatic harshness of the Tauptu; under the same circumstances, he reflected, he might become equally intense. 'Under the same circumstances'? The circumstances were the same.
The flat voice of the translation-box interrupted his thoughts. "Look."
Burke saw a Chitumih struggling ferociously as the Tauptu took him to the denopalizing grill. The nopal towered over his head and neck like some fantastic war helmet.
"You are witness to a great occasion," said Apiptix. "This is the last of the Chitumih. There are no more. Ixax is now purged."
Burke heaved a deep sigh, and with it undertook responsibility for the task the Xaxans had thrust upon him. "In time Earth will be the same. ... In time, in time . . ."
The Tauptu clamped the last Chitumih to the grill; the blue flame chattered; the Chitumih rattled like a great threshing-machine. Burke turned away sick to his stomach, sick at heart. "We can't do this!" he said hoarsely. "There must be some easy way to denopalize; we can't torture—we can't make war!"
"There is no easy way," declared the voice-box. "There shall be no delay; we are determined!"
Burke glared at him in anger and surprise. A few minutes previously Apiptix himself had suggested the possibility of a research program on Earth; now he balked at the idea of delay. A curious inconsistency I
"Come," said Apiptix abruptly. "You shall see what becomes of the nopal."
They entered a long rather dim room, ranked with benches. A hundred Xaxans worked with steady intensity, assembling mechanisms Burke could not identify. If they felt curiosity concerning Burke, he was unable to detect it.
Apiptix told Burke. "Seize the bag."
Burke obeyed gingerly. The bag felt crisp and frail; the nopal within crushed at his touch. "It feels brittle," he said, "like dry old eggshell."
"Peculiar," said Apiptix. "But do you not deceive yourself? How can you feel something which is impalpable?" Burke looked startled at Apiptix, then at the bag. How was it possible, indeed? He no longer felt the bag. It sifted through his fingers like a wisp of smoke. "I can't feel it," he said in a voice husky with astonishment.
"Certainly you can," said Apiptix. "It is there, you can sense it and you already felt it."
Burke reached out again. The bag at first seemed less tangible than before—but definitely it was there. As he gained certainty the tactile sensation increased in strength.
"Do I imagine it?" he asked. "Or is it real?"
"It is something you feel with your mind, not your hands."
Burke experimented with the bag. "I move it with my hands. I push it. I can feel the nopal crush between my fingers."
Apiptix regarded him quizzically. "Is not sensation the reaction of your brain to the arrival of neural currents? This, as I understand it, is the operation of Earth-style brains."

"I know the difference between a sensation in my hand and one in my brain," said Burke dryly.
"Do you?"
Burke started to reply, then halted.
Apiptix continued. "It is a misconception. You feel the bag with your mind, not your hands, even if the gestures of feeling accompany the act. You reach out, you receive a tactile impression. When you do not reach, you feel nothing— because normally you expect no sensation unless the act of reaching and touching is involved."
"In that case," Burke said, "I should be able to feel the nopal-cloth without use of my hands."
"You should be able to feel anything without use of your hands."
Teletactility, thought Burke: touch without use of the nerve-endings. Was not clairvoyance seeing without use of the eyes? He turned back to the bag. The nopal glared wildly from within. He conceived himself handling the sack, squeezing it. A quiver of sensation reached his mind, no more—a mere hint of crispness and lightness.
"Try to move the bag from one spot to another."
Burke exerted his mind against the bag; bag and nopal shifted easily.
"This is fantastic," he muttered. "I must have telekinetic ability!"
"It is easy with this material," said Apiptix. "The nopal is thought, the bag is thought; what can be more easily moved by the mind than thought?"
Considering the question sheerly rhetorical, Burke made no response. He watched the operators seize the bag, thrust it down on the bench, crush it flat. The nopal, disintegrated into powder, merged with the fabric of the bag.
"There is no more to be seen here," said Apiptix. "Come."
They returned to the refectory. Burke slumped gloomily upon the bench in reaction to his previous mood of zeal and determination.
"You seem dubious," Apiptix said presently. "Do you have questions?"
Burke considered. "A moment ago you mentioned something about the operation of the Earth-brain. Does the Xaxan-brain work differently?"
"Yes. Your brain is simpler and its parts are versatile. Our brains work by much more complicated means, sometimes to our advantage, sometimes not. Your brain allows you the image-forming capacity which you call 'imagination'; we lack this. We lack your ability to combine incommensurable and irrational quantities and arrive at a new truth. Much of your mathematics, much of your thought, is incomprehensible to us—confusing, frightening, insane. But we have compensatory mechanisms in our brains: built-in calculators which instantly perform the computations you consider elaborate and toilsome. Instead of imagining—'imaging' —an object, we construct an actual model of the object in a special cranial sac. Certain of us can create very complicated models. This capacity is slower and more cumbersome than your imagination, but equally useful. We think, we conceive, we observe the universe in these terms: the model which forms in our mind and which we can feel with our internal fingers."
Burke reflected a moment. "When you equate the nopal to thought—do you mean Earth-thought or Xaxan-thought?"
Pttdu Apiptix hesitated. "The definition is too general. I used it in a broad sense. What is thought? We do not know. The nopal are invisible and impalpable, and when denied their own freedom of motion can easily be manipulated telekinetically. They feed on mental energy. Are they actually the stuff of thought? We do not know."
"Why do you not merely pull the nopal away from the brain? Why is the torture necessary?"
"We have tried to do this," said Apiptix. "We dislike pain as much as you. It is impossible. The nopal, in a final malignant fit, kills the Chitumih. On the denopalization grid we cause it so much pain that it withdraws its taproots, and so may be jerked loose. Is this clear? What else do you wish to know?"
"I'd like to know how to denopalize Earth without stirring up a hornet's nest."
"There is no easy way. I will give you plans and diagrams for the denopalizing machine; you must build one or more, and start purging your people. Why do you shake your head?"
"It's a vast project. I still feel that there must be some easier way."
"There is no easy way."
Burke hesitated, then said, "The nopal are loathsome and parasitical, that's agreed. Otherwise, what harm do they do?"
Pttdu Apiptix sat like a man of iron, cabochon eyes fixed on Burke—forming an inter-cranial model of his face and head, Burke now knew.
"They may prevent us from developing our psionic abilities," Burke went on. "This, of course, I know nothing about, but it seems—"
"Forget your misgivings," said the Xaxan's voice-box with a menacing deliberation. "There is one great fact: we are Tauptu, we will not become Chitumih again. We do not wish to submit to torture once a month. We want your cooperation in our war against the nopal, but we do not need it. We can and will destroy the nopal of Nopalgarth unless you destroy them yourself."
Once again Burke thought that it would be hard to feel friendship toward a Xaxan.
"Do you have any other questions?"
Burke considered. "I may not be able to read the plans for the denopalizing machine."
"They have been adapted to your system of units and use many of your standard components. You will find no difficulty."
"I'll need money."
"There will be no lack. We will supply you with gold, as much as you need. You must arrange to sell it. What else do you wish to know?"
"A matter which puzzles me—perhaps it's rather trivial .."
"What is it that puzzles you?"
"Simply this. To dislodge the nopal you use fabric made from dead nopal. Where did the first piece of nopal-cloth come from?"
Apiptix stared fixedly from his mud-colored eyes. The voice-box muttered something incomprehensible. Apiptix rose to his feet. "Come, you now will return to Nopalgarth."
"But you haven't answered my question."
"I do not know the answer."
Burke wondered at the leaden quality to the voice from the supposedly expressionless translation-box.

VII
they returned to Earth in a comfortless black cylinder, battered from a hundred and fifty years of service. Pttdu Apiptix refused to discuss the means of propulsion except to speak vaguely of anti-gravity. Burke recalled the disk of anti-gravitic metal which—so long ago!—had enticed him to the house of Sam Gibbons in Buellton, Virginia. He tried to steer Pttdu Apiptix into a general discussion of anti-gravity, without success. So laconic, in fact, was the Xaxan that Burke wondered whether the subject might not be an equal mystery to both of them. He broached other topics, hoping to learn the extent of Xaxan knowledge, but Pttdu Apiptix for the most part refused to satisfy his curiosity. A secretive, taciturn, humorless race, thought Burke—then reminded himself that Ixax lay ruined after a century of ferocious war, a situation not conducive to cheery good-nature. Sadly he wondered what lay ahead for Earth.
Days passed and they approached the Solar System, a spectacle which remained invisible to Burke; there were no ports except in the control room from which he had been barred. Then, while he sat puzzling over the denopalization plans, Apiptix appeared, and with a brusque motion gave Burke to understand that the moment of disembarkation had arrived. He led Burke aft, into a tender as battered and corroded as the mother-ship. Burke was astonished to find his car clamped in the hold of the tender.
"We have monitored your television broadcasts," Apiptix told him. "We know that your automobile, left neglected, would arouse attention adverse to our plans."
"What of Sam Gibbons, the man you killed?" Burke asked tartly. "Do you think he won't attract attention?"
"We removed the body. The fact of his death remains uncertain."
Burke snorted. "He disappeared the same time I did. People in my office know that he telephoned me. I'll have some explaining to do if anyone puts two and two together."
"You must use your ingenuity. I advise you to avoid the company of your fellows as much as possible. You are now a Tauptu among Chitumih. They will show you no mercy."
Burke doubted if the translation-box could convey the sarcastic edge to the comment which rose to his lips, and so restrained it.

The cylinder settled upon a quiet dirt road in the country; Burke alighted, stretched his arms. The air seemed wonderfully sweet—the air of Earth!
Dusk had not completely gone from the evening sky; the time was perhaps nine o'clock. Crickets chirped in blackberry thickets massed alongside the road; a dog bayed from a nearby farm.
Apiptix gave Burke last instructions. The toneless voice seemed muffled and conspiratorial after the echoing corridors of the vessel. "In your car are a hundred kilograms of gold. This you must convert into legal currency." He tapped the parchment case which Burke carried. You must build the denopalizer as quickly as possible. Remember that very shortly—in a matter of a week or two—the nopal will return to your brain. You must be prepared to purge yourself. This device"—he gave Burke a small black box—"emits signals which will keep me informed of your whereabouts. If you need help or further gold, break this seal, press this button. It will put you into communication with me." With no further ceremony he turned back to the dark vessel. It rose, departed.

Burke was alone. Familiar dear old Earth! Never had he realized how deeply he loved his home-world! Suppose he had been forced to spend the rest of his life on Ixax? His heart went cold at the thought. Yet—he screwed up his face—this Earth, by his instrumentality, must flow with blood. . . . Unless he could find some better way to kill the nopal. . . .
Along a driveway, apparently leading to a nearby homestead came the bobbing flicker of a flashlight. The farmer, aroused by his dog, had stirred himself to investigate. Burke climbed into his car, but the flashlight fixed on him.
"What's goin' on here?" called a gruff voice. Burke sensed rather than saw that the man carried a shotgun. "What are you doing, mister?" The voice was unfriendly. The nopal, clasped around the farmer's head and faintly luminous, puffed and distended itself indignantly.
Burke explained that he had stopped to relieve himself. No other explanation seemed adequate to the circumstances.
The farmer made no comment, swung his light around the road, turned it back to Burke. "I advise you to get movin'. Something tells me you're here for no good, and I'd just as soon let fly with my 12-gauge as look at you."
Burke saw no reason to argue. He started the motor, drove away before the farmer's nopal prompted him to carry out the threat. In the rear-view mirror he watched the flashlight's baleful white eye diminish. Gloomily he thought, my homecoming welcome from the Chitumih . . . Lucky it wasn't worse.
The dirt road became a county black-top. The tank was low on gas and at the first village, three miles down the road, Burke pulled into a service-station. A stocky young man with a sunburned face and sun-bleached blond hair emerged from under the lube rack. The spines of his nopal sparkled like a diffraction grating in the glare of the lights along the marquee; the eye-orbs peering owlishly toward Burke. Burke saw the spines give a quick jerk; the attendant stopped short, dropping his professional grin with startling suddenness. "Yes, sir," he said gruffly.
"Fill the tank, please," said Burke.
The attendant muttered under his breath, went to the pump. When the tank was filled he took Burke's money with averted gaze, making no move to check the oil or clean the windshield. He brought the change, thrust it through the window mumbling, "Thank you, sir."
Burke inquired the best route to Washington; the youth jerked a thumb: "Follow the highway," and stalked sullenly away.
Burke chuckled sadly to himself as he turned out into the highway. A Tauptu on Nopalgarth and a snowball in hell had a lot in common, he reflected.
A big diesel truck and trailer roared past. With sudden alarm Burke wondered about the driver and the driver's nopal, both peering ahead along the headlight-washed road. How much influence could the nopal exert? A twitch of the hand, a jerk of the steering-wheel . . . Burke drove hunched over the wheel, sweating at each set of oncoming headlights.
Without incident or accident he came to the outskirts of Arlington, where he lived in an unpretentious apartment. A gnawing at the stomach reminded him that he had eaten nothing for eight hours, and then only a bowl of Xaxan porridge. In front of a brightly-lit sandwich-and-malt shop he slowed and halted, looked uncertainly through the windows. A group of teen-agers lounged in knotty-pine booths; two young laborers in 'Frisco jeans sat hunched over hamburgers at the counter. Everyone seemed preoccupied with his own affairs, although all the nopal in the room shimmered nervously and peered out the window toward Burke. Burke hesitated, then in a fit of obstinacy, parked his car, entered the soda fountain, and seated himself at the end of the counter.

The proprietor came forward wiping his hands on his apron, a tall man with a face like an old tennis ball. Above the white chefs hat rose a magnificent plume of spines, four feet tall, glossy and thick. The eyes beside his head were as large as grapefruit. This was the largest and finest nopal Burke had yet seen.
Burke ordered a pair of hamburgers in a voice as neutral and unprovocative as he could manage. The proprietor half-turned away, then stopped, inspecting Burke sidewise. "What's the trouble, buddy? You drunk? You act kinda funny."
"No," said Burke politely. "I haven't had a drink for weeks."
"You hopped up?"
"No," said Burke with an edgy grin. "Just hungry."
The proprietor turned slowly away. "I don't need no wisecracks. I got trouble enough without smart-alecks."
Burke held his tongue. The proprietor petulantly slapped meat down on the griddle, and stood looking over his shoulder at Burke. His nopal seemed to have swiveled around so that it too stared at Burke.
Burke turned his head to find nopal-eyes watching from the knotty-pine booths. He looked up toward the ceiling; three or four nopal drifted across his line of sight, airy as milk-weed floss. Nopal everywhere: nopal large and small; pink and pale green; nopal like shoals of fish; nopal behind nopal, down distances and perspectives that receded far beyond the walls of the room. . . . The outer door swung open; four husky youths swaggered in and took seats next to Burke. From their conversation Burke gathered that they had been driving around town hoping to pick up girls, but without success. Burke sat quietly, conscious of a nopal's rolling orb nauseatingly close to his face. He shrank away a trifle; as if at a signal the young man beside him turned, stared coldly at him. "Something bothering you, chum?"
"Nothing whatever," said Burke politely.
"Sarcastic bastard, ain'tcha?"
The proprietor loomed over them. "What's the trouble?"
"Just this guy acting sarcastic," said the youth, drowning out Burke's remarks.
A foot from Burke's head the nopal's eyes bobbed and ogled. All the other nopal in the room watched intently. Burke felt lonely and isolated. "I'm sorry," he said evenly. "I meant no offense."
"Would you like to settle it outside, chum? I'd be glad to help."
"No, thanks."
"Kinda chicken, ain'tcha?"
"Yep."
The youth sneered, turned his back.
Burke ate the hamburgers which the proprietor spun contemptuously down before him, paid his check, went out the door. Behind came the four youths. Burke's adversary said, "Look, chum, I don't wanta be insulting, but I don't like your face."
"I don't like it either," said Burke, "but I've got to live with it."
"With your fast line you oughta go on TV. You got a real wit."
Burke said nothing, but tried to walk away. The offended young man jumped in front of him. "About that face of yours —since neither of us like it—why don't I change it a little?" He swung his fist; Burke ducked. Another of the group pushed him from behind; he stumbled and the first hit him a hard blow. He fell to the graveled driveway; the four began kicking him. "Get the son of a bitch," they hissed, "get him good."
The proprietor rushed out. "Cut it out! Hear me? Stop it! I don't care what you do, only don't do it here!" He addressed Burke, "Get up, get goin', and don't come back, if you know what's good for you!"
Burke limped to his car, got in. In front of the soda fountain the five looked after him. He started the car, drove slowly to his apartment, body throbbing from his new aches and bruises. A fine homecoming, he thought with bitterly amused self-pity.

He parked his car in the street, stumbled up the stairs, opened his door, and limped wearily inside.
He stood in the center of the room looking around at the comfortably shabby furniture, the books, mementoes, general odds and ends. How dear and familiar these things were; how remote they had become. It was as if he had wandered into a room of his childhood. . . .
In the hall, footsteps sounded. They stopped outside his door; there was a timid tap. Burke grimaced. This would be Mrs. McReady, his landlady, who was impeccably genteel, but on occasion talkative. Tired, bruised, discouraged and disheveled, Burke was in no mood for spurious politeness.
The tap sounded again, rather more insistent. Burke could not ignore it; she knew he was home. He limped over to the door, swung it open.
In the hallway stood Mrs. McReady. She lived in one of the first floor apartments. A frail nervously energetic woman of sixty, with well-brushed white hair, a delicate face and a fresh complexion on which, so she claimed, she used nothing but Castile soap. She carried herself erectly, spoke clearly and with precision; Burke had always regarded her as a charming Edwardian survival. The nopal riding her shoulders appeared grotesquely large. Its bank of spines rose pompous and arrogant, almost as tall again as Mrs. McReady. Its thorax was a great wad of dead-black fuzz, its sucker-flap almost enveloped her head. Burke was sickened and astounded: how could so slight a woman support so monstrous a nopal?
Mrs. McReady in her turn was surprised by Burke's battered appearance. "Mr. Burke! What on earth has happened? Did you"—her voice dwindled and the last words fell out one at a time—"have some kind of accident . . . ?"
Burke tried to reassure her with a smile. "Nothing serious. A mix-up with a gang of hoodlums."
Mrs. McReady stared, and from just below her ears the great orbs of the nopal peered at Burke. Her face became rather pinched. "Have you been drinking, Mr. Burke?"
Burke protested with an uneasy laugh. "No, Mrs. McReady —I'm not drunk and disorderly."
Mrs. McReady sniffed. "You really should have left word of some sort, Mr. Burke. Your office has called several times, and men have been here inquiring for you—policemen, I should think."
Burke explained that matters beyond his control had made normal procedures impossible, but Mrs. McReady paid no heed. She was now quite disturbed by Burke's carelessness and lack of consideration; she had never thought Mr. Burke such a—yes, such a boor!
"Miss Haven also has telephoned—almost every day. She's been terribly worried by your absence. I promised to let her know as soon as you arrived."
Burke groaned between clenched teeth. It was unthinkable that Margaret should be involved in this business! He put his hands to his head, smoothed his rumpled hair, while Mrs. McReady watched with suspicion and disapproval.
"Are you ill, Mr. Burke?" She put the inquiry not from sympathy but out of her creed of dynamic kindness, which made her the terror of anyone she found abusing an animal.
"No, Mrs. McReady, I'm quite all right. But please don't call Miss Haven."
Mrs. McReady refused a commitment. "Good night, Mr. Burke." She marched stiff-backed down the steps, upset and disgusted by Mr. Burke's behavior. She'd always thought him so pleasant and reliable! Directly to the telephone she went, and as she had promised, telephoned Margaret Haven.
Burke mixed himself a highball, drank it without pleasure. He soaked under a hot shower, gingerly shaved. Then, too tired and miserable to worry about his problems, crawled into bed and slept.

Shortly after dawn he awoke and lay listening to the morning sounds: the whir of an occasional early automobile, a distant alarm-clock abruptly cut off, the twitter of sparrows: all so normal as to make his mission seem absurd and fantastic. Still—the nopal existed. He could see them drifting on the cool morning air like enormous big-eyed mosquitoes. Fantastic though the nopal might be, they were by no means absurdities. According to Pttdu Apiptix he could count on no more than a further two weeks of grace. Then the nopal would overcome whatever resistance now existed and once again he would be chitumih . . . Burke shuddered, sat quickly up on the edge of his bed. He would become as cold and hard as the Xaxans; he would go to any length rather than become afflicted again; he would spare no one, not even—the doorbell rang. Burke tottered to the door, eased it open, dreading to see the face he knew would be there.
Margaret Haven faced him. Burke could not bear to look at the nopal clinging to her head. "Paul," she said huskily, "what on earth is the matter with you? Where have you been?"
Burke took her hand, drew her into the apartment. With a leaden heart he felt the fingers become stiff and rigid. "Make some coffee," he said in a dreary voice. "I'll get some clothes on."
Her voice followed him to the bedroom. "You look as if you'd been on a month-long drunk."
"No," he said. "I've been having, let us say, some remarkable adventures."
He joined her five minutes later. Margaret was tall and long-legged, with an attractive tomboy abruptness of movement. In a crowd, Margaret was inconspicuous. But looking at her now Burke thought he had never known anyone more appealing. Her hair was dark and unruly, her mouth wide with a Celtic twitch at the corners, her nose crooked from a childhood automobile accident. But taken together her features produced a face of startling vivacity and expressiveness, where every emotion showed as clear as sunlight. She was twenty-four years old, and worked in an obscure division of the Department of the Interior. Burke knew her to be without guile, and as innocent of malice as a kitten.
She watched him with a puzzled frown. Burke realized that she was awaiting some explanation for his absence, but try as he might, he could think of no convincing story. Margaret, for all her own guilelessness, was instantly aware of falsity in others. So Burke stood in the living room, sipping coffee, refusing to meet Margaret's eye.
Finally, in an attempt at decisiveness, he said, "I've been gone almost a month, but I can't tell you where I've been."
" 'Can't' or 'won't'?"
"A little of both. It's something I've got to make a mystery of."
"Government business?"
"No."
"You're not—in some kind of trouble?"
"Not the kind you're thinking of."
"I wasn't thinking of any particular kind."
Burke flung himself moodily down into a chair. "I haven't been off with a woman or smuggling in dope."
She shrugged, and seated herself across the room. She inspected him with a clear dispassionate gaze. "You've changed. I can't quite understand how—or why—but you've changed."
"Yes. I've changed."
They sat drinking coffee in silence. Margaret presently asked, "What are you going to do now?"

"I'm not going back to my job," said Burke. "I'm resigning today, if I'm not already fired. . . . Which reminds me—" He stopped short. He was about to say that he had a hundred kilograms of gold in the back of his car, worth roughly a hundred thousand dollars, and that he hoped no one had stolen it.
"I wish I knew what was wrong," said Margaret. Her voice was calm, but her fingers trembled and Burke knew she was near to tears. Her nopal watched placidly, with no show of feeling other than a slow pulsation of its spines. "Things aren't as they were," she said, "and I don't know why. I'm confused."
Burke drew a deep breath. He gripped the arms of the chair, rose to his feet, crossed to where she sat. Their gazes met. "Do you want to know why I can't tell you where I've been?"
"Yes."
"Because," he said slowly, "you wouldn't believe me. You'd think I was a lunatic and have me committed—and I don't want to spend any time in an asylum."
Margaret made no immediate response. She looked away, and Burke could read on her face the startling speculation that perhaps Burke indeed was crazy. Paradoxically, the thought gave her hope: Paul Burke crazy was no longer mysterious, tight-lipped, surly, hateful Paul Burke, and she looked back at him with renewed hope.
"Are you feeling well?" she asked timidly.
Burke took her hand. "I'm perfectly well and perfectly sane. I've got a new job. It's tremendously important—and we can't see each other any more."
She snatched her hand away. Pure detestation flashed from her eyes, mirroring the hate staring at him in the eye-globes of the nopal. "Very well," she said in a thick voice. "I'm glad you feel this way—because I do too."
She turned and ran from the apartment.
Burke drank his coffee thoughtfully, then went to the telephone. His first call brought him the information that Dr. Ralph Tarbert had already left for his Washington office.
Burke poured himself another cup of coffee, and after half an hour called Tarbert's office.
The secretary took his name; ten seconds later Tarbert's level voice sounded in the ear-piece. "Where in thunder have you been?"
"It's a long bitter story. Are you busy?"
"Nothing overwhelming. Why?"
Had Tarbert's tone changed? Could his nopal smell out a Tauptu across fifteen miles of city? Burke could not be sure; he was becoming hyper-sensitive and no longer trusted his own judgment. "I've got to talk to you. I guarantee you'll be interested."
"Good," said Tarbert. "Are you coming down to the office?"
"I'd prefer that you come here, for several very good reasons." Principally, thought Burke, I don't dare to leave the apartment.
"Hmm," said Tarbert carelessly. "This sounds mysterious, even sinister."
"It's all of that."
The wire was silent. Presently Tarbert remarked in a cautious voice, "I assume that you've been ill? Or injured?"
"Why do you assume that?"
"Your voice sounds strange."
"Even over the phone, eh? Well, I am strange. Unique, in fact. I'll explain when I see you."
"I'm coming immediately."

Burke sat back in a mixture of relief and apprehension. Tarbert, like everyone else of Nopalgarth, might hate him so fervently as to refuse to help him. It was a delicate situation, one which required the most careful handling. How much to tell Tarbert? How much could Tarbert's credulity ingest at a gulp? Burke had brooded hours over this particular question, but still had come to no decision.
He sat quietly looking out the window. Men and women walked the sidewalks . . . Chitumih, oblivious to their complacent parasites. It seemed that, as they passed, all the nopal peered up at him—although this might be his imagination. He still had no certainty that the doorknob-size orbs functioned as eyes. He searched the sky: the filmy forms were everywhere, floating wistfully over the throngs, envious of their more fortunate fellows. Focusing his mental gaze, Burke saw ever greater numbers, many surrounding him, eyeing him hungrily. He looked through the air of the room: two, three; no four! He rose, went to the table where he had laid his case, opened it, took out a wisp of nopal-cloth. Forming it into a bag, he waited his opportunity, lunged. The nopal slipped away. Burke tried again, again the nopal darted aside. They were too quick for him; they moved like balls of quicksilver. And even if he caught one and crushed it, what then? One nopal subtracted from the billions infesting the planet: a process as futile as stepping on ants.
The doorbell rang; Burke crossed the room cautiously opened the door. Ralph Tarbert stood in the hall, elegant in gray sharkskin, a white shirt, a black polka-dot tie. No casual observer could have guessed his occupation. Boulevardier, drama critic, avant-garde architect, successful gynecologist, yes; one high in the ranks of the world's scientists, never. The nopal riding his head was not extraordinary, by no means as fine as Mrs. McReady's. Evidently the mental quality of the man was not reflected in the style of his nopal. But the eye-orbs stared as balefully as any Burke had encountered.
"Hello, Ralph," said Burke with guarded cordiality. "Come in."
Tarbert entered warily. The nopal jerked its spines and shimmered in anger.
"Coffee?" asked Burke.
"No thanks." Tarbert looked curiously around the room. "On second thought, yes. Black, as I'm sure you remember."
Burke filled a cup for Tarbert and refilled his own. "Sit down. This is going to take a bit of time." Tarbert settled himself in a chair; Burke took a place on the couch.
"First," said Burke, "you've come to the conclusion that I've undergone some searing experience which has completely changed my personality."
"I notice a change," Tarbert admitted.
"For the worse, I should imagine?"
"If you insist, yes," Tarbert said politely. "I can't quite identify the precise quality of the change."
"However, you now decide that you dislike me. You wonder why you became friendly with me in the first place."
Tarbert smiled thoughtfully. "How can you be so certain of all this?"
"It's part of the whole situation; a very important part. I mention it so that you can discount it in advance and perhaps ignore it."
"I see," said Tarbert. "Go on."
"I'll eventually explain everything to your complete satisfaction. But until I do you've got to summon all your professional objectivity, and put this peculiar new dislike for me to the side. We can stipulate that it exists—but I assure you it's artificial in origin, something outside us both."
"Very well," said Tarbert. "I'll put a rein on my emotions. Continue. I'm listening—intently."

Burke hesitated, carefully choosing his words. "In the broadest outline my story is this: I've stumbled upon an entirely new field of knowledge, and I need your help in exploring it. I'm handicapped by this aura of hate I carry with me. Last night I was attacked in the street by strangers; I don't dare show myself in public."
"This field of knowledge to which you refer," Tarbert asked cautiously, "apparently it's psychic in nature?"
"To a certain degree. Although I'd prefer not to use that particular word; it carries too many metaphysical connotations. I haven't any idea what kind of terminology applies. 'Psionic' is better." Noting Tarbert's carefully composed expression, he said, "I didn't bring you here to discuss abstract ideas. This business is about as psychic as electricity. We can't see it, but we can observe its effects. This dislike which you feel is one of the effects."
"I don't feel it any longer," mused Tarbert, "now that I've tried to pin it down. ... I notice a physical sensation, something of a headache, a touch of nausea."
"Don't ignore it because it's still there," said Burke. "You've got to be on your guard."
"Very well," said Tarbert, "I'm on my guard."
"The source of all this is a"— Burke groped for a word —"a force which I have temporarily escaped, and which now considers me a threat. This force works on your mind, hoping to dissuade you from helping me. I don't know what pressures it will use, because I'm not sure how intelligent it is. It has enough awareness to know that I am a threat."
Tarbert nodded. "Yes. I feel that. I feel the impulse, oddly enough, to kill you." He smiled. "On the emotional, not the rational level, I'm glad to say. I'm intrigued. . . . I never realized such things could be."
Burke laughed hollowly. "Wait till you hear the whole thing. You'll be much more than intrigued."
"The source of this pressure, is it human?"
"No."
Tarbert rose from his chair, took a more comfortable position on the couch beside Burke. His nopal fluttered and squirmed and glared. Tarbert glanced sidewise, raising his fine white eyebrows. "You moved away from me. Do you feel this same dislike toward me?"
"No, not at all. Look on that table there; notice that folded piece of cloth."
"Where?"
"Right here."
Tarbert squinted. "I seem to see something. I can't be sure. Something indistinct and vague. It gives me the shudders, somehow—like fingernails on a blackboard."
"You should be reassured," said Burke. "If you can feel the same quality of emotion toward a piece of cloth as you do toward me, then you must realize the emotion has no rational basis."
"I realize this," said Tarbert. "Now that I'm aware of it I can keep it under control." Something of his brittle urbanity had departed, laying bare the earnest personality he chose to camouflage. "Now there's a peculiar snarling sound in my mind: 'grr,' 'grr,' 'grr.' Like gears clashing, or someone clearing his throat. . . . Odd. 'Gher' is more like it; a glottal 'gher.' Is that telepathic, by any chance? What is 'gher'?"
Burke shook his head. "I've no idea. I've heard the same thing."
Tarbert gazed off into space, then closed his eyes. "I see peculiar flitting images—odd things, rather repulsive. I can't make them out. . . ." He opened his eyes, rubbed his forehead. "Strange . . . Do you perceive these—visions?"
"No," said Burke. "I merely see the real thing."
"Oh?" Tarbert stared. "You amaze me. Tell me more."

"I want to build a rather sizable piece of equipment. I need a private site, safe from intruders. A month ago I could have selected among a dozen laboratories; now I can't get cooperation anywhere. In the first place, I'm terminated with ARPA. In the second place everyone on Earth now hates my guts."
'Everyone on Earth,' " Tarbert mused. "Does that imply that someone not on Earth does not hate you?"
"To a certain extent. You'll know as much as I do inside of a week or two, and then you'll have a choice—just as I had—whether to proceed with the matter or not."
"Very well," said Tarbert. "I can promote a workshop for you; in fact Electrodyne Engineering leaps to mind. They're closed down, the whole plant is vacant. You probably know Clyde Jeffrey?"
"Very well."
"I'll speak to him; I'm sure he'll let you use the place as long as you like."
"Good. Can you call him today?"
"I'll call him right now."
"There's the phone."
Tarbert telephoned, and immediately secured informal permission for Burke to use the premises and equipment of the Electrodyne Engineering Company for as long as he wished.
Burke wrote Tarbert a check. "What's this for?" asked Tarbert.
"That's my bank-balance. I'll need supplies and material. They'll have to be paid for."
"Twenty-two hundred bucks won't buy very much."
"Money is the least of my worries," said Burke. "There's a hundred kilograms of gold in the back of my car."
"Good Lord!" said Tarbert. "I'm impressed. What do you want to build at Electrodyne? A machine to make more gold?"
"No. Something called a denopalizer." Burke watched Tarbert's nopal as he spoke. Did it comprehend his words? He could not be sure. The bank of spines wavered and shimmered, which might mean much or nothing.
"What is a 'denopalizer'?"
"You'll soon know."
"Very well," said Tarbert. "I'll wait, if I must."

VIII
Two days later Mrs. McReady knocked at the door to Burke's apartment—a knock delicate and ladylike, but nevertheless firm. Burke rose gloomily to his feet, opened the door.
"Good morning, Mr. Burke." Mrs. McReady spoke with frigid courtesy. Her grotesquely large nopal puffed out at him like a turkey gobbler. "I'm afraid I have unpleasant news for you. I find that I will be needing your apartment. I will appreciate your locating another residence as quickly as possible."
Burke nodded sadly. The request came as no surprise; in fact he had already furnished a corner of the Electrodyne Engineering workshop with a cot and a gasoline stove. "Very well, Mrs. McReady. I'll be out in a day or so."
Mrs. McReady's conscience plainly troubled her. If only he had made a scene, or acted disagreeably, she could have justified her action to herself. She opened her mouth to speak, then, uncertainly, said only, "Thank you, Mr. Burke." Burke returned slowly into his living room.

The episode followed the pattern he had come to expect. Mrs. McReady's formality represented an antagonism no less intense than the physical attack of the four hoodlums. Ralph Tarbert, dedicated by profession and temperament to objectivity, admitted that he continually struggled against malice. Margaret Haven had telephoned in great trouble and anxiety. What was wrong? The loathing she suddenly felt for Burke she knew to be unnatural. Was Burke ill? Or had she herself become afflicted with paranoia? Burke found it hard to answer her, and wrestled with himself for wordless seconds. He could bring her nothing but grief, of one kind or another; this was certain. By every precept of decency he should force a clean break between them. In halting words he tried to put this policy into effect, but Margaret refused to listen. No, she declared, something external was responsible for their trouble; together they would defeat it.
Burke, oppressed by his responsibility and by sheer loneliness, could argue no further. He told her that if she'd come to the Electrodyne Engineering plant—this particular call took place the day after Mrs. McReady had asked him to leave—he'd explain everything.
Margaret, in a dubious voice, replied that she'd come immediately.
A half hour later she tapped at the door to the outer office. Burke came out of the workshop, snapped back the bolt. She entered slowly, uncertainly, as if she were wading into a pool of cold water. Burke could see that she was frightened. Even her nopal appeared agitated, its bank of spines glittering with a red and green iridescence. She stood in the middle of the room, emotions chasing themselves back and forth across her wonderfully expressive face. Burke essayed a smile; from Margaret's expression of alarm, it conveyed no message of cheer. "Come along," he said in a false and brassy voice, "I'll show you around." In the workshop she noticed his cot and the table with the camp stove. "What's all this? Are you living here?"
"Yes," said Burke. "Mrs. McReady became afflicted with the same distaste for me which you feel."
Margaret looked at him numbly, then turned away. She became stiff and tense. "What's that thing?" she asked in a husky voice.
"It's a denopalizer," said Burke.
She cast him a frightened glance over her shoulder, while her nopal shimmered and flickered and squirmed. "What does it do?"
"It denopalizes."
"It frightens me," said Margaret. "It looks like a rack, or a torture machine."

"Don't be frightened," said Burke. "It's not a mechanism for evil, even though it seems to be."
"Then what is it?"
Now, if ever, was the time to confide in her—but he could not bring himself to speak. Why load her mind with his troubles, even assuming that she would believe him? In fact, how could she believe him? The tale was simply too far-fetched. He had been whisked to another planet; the inhabitants had convinced him that the people of Earth were all haunted by a particularly vile mind-leech. He and he alone could see these things: even now the creature which rode her shoulders glared at him full of hate! He, Burke, had been charged with the mission of exterminating these parasites; if he failed, the inhabitants of the far-away world would invade and demolish Earth. It was obvious megalomania; Margaret's certain duty would be to call an ambulance for him.
"Aren't you going to tell me?" asked Margaret.
Burke stood looking foolishly at the denopalizer. "I wish I could think of a convincing lie—but I can't. If I told you the truth, you wouldn't believe me."
"Try me."
Burke shook his head. "One thing you've got to believe: the hate you feel for me isn't either your doing or mine. It's a suggestion from something external to both of us— something that wants you to hate me."
"How can that be, Paul?" she cried in distress. "You've changed! I know you have! You're so different from what you were!"
"Yes," Burke admitted. "I've changed. Not necessarily for the worse—although it may seem so to you." He somberly inspected the denopalizing rack. "Unless I get busy I'll be changing back to what I was before."
Margaret impulsively squeezed his arm. "I wish you would!" She snatched her hand away again, took a step back, stared at him. "I can't understand myself, I can't understand you. . . ." She turned, walked rapidly from the shop into the office.
Burke heaved a weary sigh, but made no move to follow.
He checked the plans, drawn by Pttdu Apiptix in the Xaxan's crabbed rendition of English symbols, returned to work. Time was running short. Overhead at all times drifted two, sometimes three or even four nopal, waiting for whatever mysterious signal they needed before settling upon Burke's neck.
Margaret presently appeared in the doorway where she stood watching Burke. After a moment she crossed the floor of the workshop, took up Burke's coffee-pot, looked into it, wrinkled "her nose. Taking the pot into one of the lavatories, she cleaned it, filled it with water and made fresh coffee.
Ralph Tarbert had now appeared; the three drank coffee together. Margaret derived reassurance from Tarbert's presence and tried to pry information from him. "Ralph, what is a denopalizer? Paul won't tell me."
Tarbert laughed uncomfortably. "A denopalizer? A machine used to denopalize—whatever that is."
"Then you don't know either."
"No. Paul is very secretive."
"Not for long," said Burke. "Two more days, all will be made clear. Then the fun begins."
Tarbert inspected the rack, the shelves of circuitry behind, the power lead-ins. "At a guess, it's a piece of communication equipment—but whether for transmitting or receiving, I don't know."
"It frightens me," said Margaret. "Everytime I look at it something inside me squirms. I hear noises and see weird lights. Things like cans full of fishing-worms."
"I have the same sensations," said Tarbert. "Odd that a piece of machinery could affect a person like that."
"Not so very odd," said Burke.

Margaret glanced at him sidewise with a curled lip. Detestation all but threatened to swamp her self-control. "You sound absolutely sinister."
Burke shrugged, in a manner Margaret thought callous and brutal. "I don't intend to." He looked up to the nopal floating above him, something like an enormous Portuguese Man-o'-war. This particular specimen dogged him day and night, eyes staring, spines fluffing and working in a ceaseless hungry quiver. "I've got to get back to work. There's not much time."
Tarbert put down his empty cup. Watching his expression, Margaret realized that he, too, was beginning to find Burke intolerable. What had happened to the old Paul Burke, the pleasant relaxed man with the easy good-nature? Margaret wondered about brain-tumors: weren't they sometimes responsible for sudden changes in personality? She felt a rush of shame: the old Paul Burke was as he always had been; he deserved pity and understanding.
Tarbert said, "I won't come tomorrow; I'll be busy all day."
Burke nodded. "Perfectly all right. But Tuesday I'll be ready, and I'll need you. You'll be on hand?"
Margaret once again could hardly control her revulsion. Burke seemed so feral, so insane! Yes, insane! She certainly should take steps to have him examined, treated—
"Yes," said Tarbert, "I'll be on hand. How about you, Margaret?"
Margaret opened her mouth to speak, but Burke shook his head curtly. "We'd better do this by ourselves—at least on the first run."
"Why?" asked Tarbert curiously. "Is there danger?"
"No," said Burke. "Not for either of us. But a third party would complicate matters."
"Very well," said Margaret in a neutral voice. Under other circumstances her feelings would have been hurt; now, she felt nothing. This machine was probably nothing but an aberration, a senseless agglomeration of parts. . . . But if this were so, would Dr. Tarbert take Burke so seriously? Surely he'd notice any scientific irrationality—and he showed no signs that he had. Perhaps the machine was not a lunatic device after all. But if not, what was its purpose? Why should Burke wish to exclude her at the try-out?
She strolled away from Burke and Tarbert, slipped into the warehouse. Inconspicuous in a corner was an old door secured by a spring-lock Margaret drew back the bolt, secured it; the door could now be opened from the outside.
She returned into the workshop. Tarbert was taking his leave; Margaret departed with him.

She slept very poorly and worked listlessly the next day. Monday evening she telephoned Ralph Tarbert, hoping for reassurance. He was not in, and Margaret spent another uneasy night. Something told her—instinct?—that tomorrow would be a very important day. Eventually she went to sleep, but when she awoke her mind was clouded with uncertainty. She sat dull-eyed over coffee until it was too late to go to work, then telephoned that she was ill.
At noon, she tried once more to get in touch with Dr. Tarbert, but none of his associates knew where he could be found.
Driven by indefinable uneasiness, Margaret backed her car from the garage, drove southeast out Leghorn Road until a quarter-mile ahead she saw the gray blocks of Electrodyne Engineering. Beset by an unreasoning alarm she veered down a side road, accelerated and drove wildly for several miles. Then she pulled to the side of the road, and collected her wits. She was behaving erratically, irrationally. Why on earth all these crazy impulses? And these odd sounds in her head, and the peculiar hallucinations?
She made a U-turn and drove back to Leghorn Road. At the intersection she hesitated, then gritting her teeth, turned right toward Electrodyne Engineering.

In the parking lot were Burke's old black Plymouth convertible and Dr. Tarbert's Ferrari. Margaret parked, sat a moment or two in the car. There was no sound to be heard, no voices. She gingerly alighted, and now ensued another struggle within herself. Should she make use of the main entrance, walk boldly into the general office? Or should she go around to the back and enter through the warehouse?
She chose the warehouse, and circled the building.
The door was as she had left it; she opened it, stepped into the dim interior.
She crossed the concrete floor, her footsteps seeming to echo in spite of her stealth.
Halfway to the workshop she paused weakly, like a swimmer in the middle of a lake who is uncertain of making the shore.
From the workshop came the murmur of voices, then a hoarse cry of anger—Tarbert's voice. She ran to the door, looked through.
She was right. Burke was stark staring mad. He had strapped Dr. Tarbert to the bars of his devilish machine; he had fixed heavy contacts to Tarbert's head. Now he was talking, a smile of devilish cruelty on his face. Margaret could catch only a few of his words over the pounding of the blood in her brain, "—rather less pleasant surroundings, on a planet called Ixax—" "—the nopal, as you'll see—" "—relax, now, you'll wake up tauptu—"
"Let me up from here," bellowed Tarbert. "Whatever it is, I don't want it!"
Burke, white-faced and haggard, gave him no more attention. He twisted a switch. A wavering bluish-violet glare cast flickering lights and shadows around the room. From Tarbert came an unearthly squeal of pain; he stiffened and strained at the straps.
Margaret watched in horrified fascination. Burke took up a swath of what seemed to be transparent plastic; he threw it over Tarbert's head and shoulders. An apparent rigidity in its folds distended it, held it up from the tubing behind Tarbert's head. To the intermittent flash of the crackling light and Tarbert's awful cries, Burke began working and kneading at the transparent film.
Margaret recovered her senses. Gher, gher, gher! She looked about for a weapon, a bar of iron, a wrench, anything. . . . There was nothing in sight. She half-started forth to attack him with her bare hands, thought better of it, and instead darted behind Burke into the office, where there was a telephone. Mercifully it was connected. The tone came instantly. She dialed for the operator. "Police, police," she croaked. "Get me the police!"
A gruff masculine voice spoke; Margaret stammered out the address. "There's a madman here; he's killing Dr. Tarbert, torturing him!"
"We'll send a cruiser over, miss. Electrodyne Engineering, Leghorn Road, right?"
"Yes. Hurry, hurry. . . ." Her voice choked in her throat. She felt a presence behind her; she knew a freezing fear. Slowly, her neck stiff, the vertebrae seeming to grate on each other, she turned her head.
Burke stood in the doorway. He shook his head sorrowfully, then turned, walked slowly back to where the body of Tarbert lay convulsing, pumping up and down to the flash of the weird lights. He picked up the transparent film, resumed his work—kneading, tugging around Tarbert's head.
Margaret's legs gave way; she staggered against the jamb of the door. Numbly she wondered why Burke had not injured her. He was a maniac; he must have heard her calling for the police. . . . Far away she heard the wail of a siren, swelling and singing, louder and louder.

Burke stood up. He was panting; his face was drawn and skull-like. Never had Margaret seen so evil a sight. If she had possessed a gun, she would have shot; if her knees had held her, she would have attacked with her hands. . . . Burke was holding the film bagged around something. Margaret could see nothing within; nevertheless the sack seemed to move and tremble. Her brain gave a lurch; a black blur covered the bag. . . . She was conscious of Burke stamping upon the bag—a desecration, she realized; the most hideous act of all.
The police entered; Burke threw a switch on his machine. As Margaret watched numbly the police advanced cautiously upon Burke, who stood waiting, tired and defeated.
They saw Margaret. "You all right, lady?"
She nodded, but could not speak. She sank down upon the floor and burst into wild tears. Two policemen carried her to a chair and tried to soothe her. Presently an ambulance arrived. Orderlies carried out the unconscious form of Dr. Tarbert; Burke was taken away in the police cruiser; Margaret rode in another, with a trooper driving behind in Margaret's own car.

IX
burke was ordered to the State Asylum for the Criminally Insane for observation, and there confined in a small white room with a pale blue ceiling. There was tempered glass in the windows and a lattice of steel beyond. The bed was boxed into the floor so that he could not crawl underneath; there was no provision by which he could hang himself: no hooks, brackets, electrical fixtures; even the door-hinges had sloping shoulders from which a cord or improvised rope would slide.
A small group of psychiatrists examined Burke at length. He found them intelligent but either bluff and windy or vague and tentative, as if they groped through an eternal fog of obfuscation, which might have arisen either from the difficulty of their subject or the falsity of their basic premises. In their turn, the psychiatrists found Burke articulate and polite, though they could not help but resent his air of sad derision as they applied the various tests, charts, drawings, and games by which they hoped to measure the precise degree of his abnormality.
In the end they failed. Burke's insanity refused to reveal itself in any objective manner. Nevertheless the psychiatrists concurred in an intuitive diagnosis: "extreme paranoia." They described him as "deceptively rational, his obsessions craftily veiled." So craftily veiled indeed was his abnormality (they pointed out) that only trained psychopathologists like themselves could have recognized it. They reported Burke to be listless and withdrawn, with little interest in anything except the condition and whereabouts of his victim, Dr. Ralph Tarbert, whom he made repeated requests to see—requests which, of course, were denied. They required a further period in which to study Burke before making a definite recommendation to the court.
The days went on and Burke's paranoia appeared to intensify. The psychiatrist noted symptoms of persecution. Burke gazed wildly around his chamber as if following floating shapes. He refused to eat and grew thin; he feared the dark so strongly that a night light was allowed him. On two occasions he was observed beating at the empty air with his hands.
Burke was suffering not only mentally but physically. He felt a constant tugging and twisting inside his brain—a sensation similar to his original denopalization, although mercifully less intense. The Xaxans had not warned him of these torments. If they were forced to submit to them once a month, in addition to the brilliant agonies of denopalization, Burke could sympathize with their determination to expunge the nopal from the universe.
The working at his mind grew ever more violent. He began to fear himself half-crazed in actuality. The psychiatrists propounded solemn questions, inspecting him owlishly, while the nopal riding in and out of the room on their shoulders watched with an almost equal degree of bland wisdom. The staff physician at last ordered sedation, but Burke resisted, fearing sleep. The nopal hung close above, staring into his eyes, the spines fluffing and jerking and spreading, like a chicken bathing in the sand. The physician called orderlies, Burke was grasped, the needle shoved home, and in spite of his furious determination to stay awake, he lapsed into stupor.
Sixteen hours later he awoke, and lay listlessly gazing at the ceiling. His headache had gone, he felt sodden and stuffy, as if sick with a cold. Recollections came slowly, in reluctant fragments. He raised his eyes, searched the air above his bed. No nopal could be seen—to his intense relief. He sighed, lay back on the pillow.
The door opened, an orderly wheeled in a cart with a tray of food.
Burke sat up, looked at the orderly. No nopal. The space over the man's head was vacant; no baleful orbs stared down across the white-jacketed shoulders.
A thought came to Burke; he hunched back down. Slowly he raised his hand, felt the back of his neck. Nothing but his own skin and the bristle of his own hair....

The orderly stood watching him. Burke seemed quieter, almost normal. The staff psychiatrist, making his rounds, received the same impression. He held a short conversation with Burke, and could not escape the conviction that Burke had returned to normal. He therefore kept a promise he had made a few days earlier and telephoned Margaret Haven, informed her that she might visit Burke during the regular visiting hours.
That same afternoon Burke was notified that Miss Margaret Haven had come to see him. Burke followed the orderly to the cheerful waiting room, so deceptively like the lobby of a country hotel.
Margaret ran across the room, seized his two hands. She searched his face, and her own face, wan and thin, lit up with happiness. "Paul! You're back to normal! I know! I can tell!"
"Yes," said Burke, "I'm my own self again." They sat down. "Where's Ralph Tarbert?" he asked.
Margaret's gaze wavered. "I don't know. He dropped out of sight as soon as he had left the hospital." She squeezed Burke's hands. "I'm not supposed to talk of things like that; the doctor doesn't want me to excite you."
"Considerate of him. How long do they plan to keep me here?"
"I don't know. Until they make up their minds about you, I suppose."
"Hmph. They can't keep me here forever, unless they get a formal commitment of some kind...."
Margaret turned her gaze aside. "As I understand it, the police have washed their hands of the case. Dr. Tarbert has refused to bring charges against you; he insists that you and he were conducting an experiment. The police think he's just as—" She stopped short.
Burke laughed shortly. "Just as crazy as I am, eh? Well, Tarbert's not crazy. It happens that he's telling the truth."
Margaret leaned forward, her face full of doubt and anxiety. "What's going on, Paul? You're doing something strange —it's not just government work, I'm sure of that! And whatever it is, it worries me!"
Burke sighed. "I don't know. . . . Things have changed. Perhaps I was crazy; perhaps I spent a month involved in the strangest conceivable delusion. I'm not sure."
Margaret looked away, and said in a low voice, "I've been wondering whether I acted correctly in calling the police. I thought you were killing Dr. Tarbert. But now"— she made a small nervous gesture—"now I don't know."
Burke said nothing.
"You're not going to tell me?"
Burke grinned wanly, shook his head. "You'd think I was crazy for sure."
"You're not angry with me?"
"Of course not."
The bell signaling the end of visiting hours rang; Margaret rose to her feet. Burke kissed her, and noticed that her eyes were moist. He patted her shoulder. "Someday I'll tell you the whole story—perhaps as soon as I'm out of here."
"You promise, Paul?"
"Yes. I promise."
The next morning Dr. Kornberg, the institution's head psychiatrist, looked in on Burke during his routine weekly check. "Well, Mr. Burke," he asked bluffly, "how are you getting along?"
"Very well," said Burke. "In fact I'm wondering when I can be released."
The psychiatrist donned the quizzical noncommittal expression with which he met this sort of question. "When we feel that we know what, if anything, is wrong with you. Frankly, Mr. Burke, you're a puzzling case."
"You're not convinced that I'm normal?"

"Ha ha! We can't make snap decisions merely on the basis of impressions! Some of our most disturbed people appear disarmingly normal. I don't refer to you, of course—although you still exhibit a few rather puzzling symptoms."
"Such as?"
The psychiatrist laughed. "That's giving away professional secrets. 'Symptoms' perhaps is too strong a word." He considered. "Well, let's face it man to man. Why do you study yourself in the mirror five minutes at a time?"
Burke grinned painfully. "Narcissism, I suppose."
The psychiatrist shook his head. "I doubt it. Why do you grope at the air over your head? What do you expect to find?"
Burke rubbed his chin thoughtfully. "You apparently caught me at a yoga exercise."
"I see." The psychiatrist hoisted himself to his feet. "Well, well."
"Just a minute, doctor," said Burke. "You don't believe me, you think me either facetious or craftily evasive; in either case, still paranoid. Let me ask you a question. Do you consider yourself a materialist?"
"I subscribe to none of the metaphysical religions, which includes—or excludes—them all, I suppose. Does that answer your question?"
"Not entirely. What I'm after is this: Can you admit the possibility of events and experiences which are—well, out of the ordinary?"
"Yes," said Kornberg warily, "to a certain extent."
"And a man who had participated in one of these extraordinary events, and described it might well be considered insane?"
"Yes, certainly," said Kornberg. "However, if you notified me that you had recently seen a blue giraffe on roller skates playing a harmonica, I wouldn't believe you."
"No, because it would be an absurdity, a burlesque of normality." Burke hesitated. "I won't go any farther—since I want to get out, of here as soon as possible. But these actions you've observed—the looking into the mirror, feeling the air—all stem from circumstances which I regard as —well, remarkable."
Kornberg laughed. "You're certainly cautious."
"Naturally. I'm talking to a psychiatrist at the lunatic asylum, who already considers me aberrated."
Kornberg abruptly rose to his feet. "I've got to be on my rounds."
Burke took care not to examine himself in the mirror, not to feel the air over his shoulders. A week later he was released from the asylum. All charges against him had been dropped; he was a free man.
Dr. Kornberg shook hands with him on his departure. "I'm curious as to the 'remarkable circumstances' you mentioned."
"I am, too," said Burke. "I'm going out now to investigate them. Perhaps you'll have me back before long."
Kornberg shook his head in wry admonition; Margaret took Burke's arm, led him to her car. Here she hugged him, kissed him enthusiastically. "You're out! You're free, you're sane, you're—"
"Unemployed," said Burke. "Now I want to see Tarbert. Instantly."
Margaret's face, a water-clear mirror for her every emotion, displayed disapproval. She said with all-too-transparent airiness, "Oh, let's not bother with Dr. Tarbert. He's busy with his own affairs."
"I've got to see Ralph Tarbert."
Margaret stammered uncertainly, "Don't you think—well, let's go somewhere else."
Burke smiled sardonically. Evidently Margaret had been instructed—or had decided for herself—that it would be best to steer Burke away from Tarbert.
"Margaret," he said softly, "you're fooling with something you don't understand. I've got to see Tarbert."

Margaret cried in distress, "I don't want you to be involved again . . . Suppose you—well, get all excited again!"
"I'll get much more excited if I don't see Tarbert. Please, Margaret. Today I'll explain everything."
"It's not only you," said Margaret miserably. "It's Dr. Tarbert. He's changed! He was so—well, civilized, and now he's savage and bitter. Actually, Paul, I'm afraid of him. He seems evil!"
"I'm sure he isn't. I've got to see him."
"You promised to tell me how you got in that terrible situation."
"So I did." Burke heaved a deep sigh. "I'd like to keep you uninvolved as long as possible. But I promised and— let's go see Tarbert. Where is he?"
"At Electrodyne Engineering. He moved in when you left. He's become very queer."
"I don't wonder," said Burke. "If all this is real—if I'm not a real maniac—"
"Don't you know?"
"No," said Burke. "I'll find out from Tarbert. I hope I'm crazy. I'd be relieved and happy if I could believe I were."
Margaret's face showed her shock and bewilderment; nevertheless, she said no more.
They drove slowly out Leghorn Road, Margaret's reluctance to proceed becoming ever more marked. And Burke himself began to find reasons why visiting Tarbert was a poor idea. His brain flashed with crackles of pale light, sounded to a sibilant hiss, and there was a sensation almost like a thud in his auditory centers. A thud, a growl. "Gher —gher—gher—" the sound he had heard before, on Ixax. Or was Ixax an illusion, and he himself insane? Burke fretfully shook his head. The whole affair was insane. Impelled by some wild delusion he'd tied poor Tarbert to his homemade torture machine and no doubt nearly killed him. Tarbert might be difficult, even unpleasant. . . . He definitely had no wish to see Tarbert. The closer they approached Electrodyne Engineering, the stronger grew his reluctance, and the louder grew the grating sound in his mind: "Gher —gher—gher." The glimmer of light in his brain increased in intensity, swam before his eyes like visions. He saw blooming dark colors, an object repellently like a drowned woman floating deep in a black-green ocean, her long pale hair floating free. . . . He saw waxy sea-weed crusted with colored stars, like blossoms on a hollyhock. He saw a vat of churning spaghetti the strands drawn from quaking blue-green glass. . . . Burke drew in his breath with a hiss, wiped his eyes with the back of his hand.
Margaret looked hopefully toward him with each of his uneasy movements—but Burke clamped his mouth obstinately. When he saw Tarbert he'd know the truth. Tarbert would know.
Margaret drove into the parking lot. There was Tarbert's car. On leaden feet Burke walked toward the door to the office. The growl inside his brain was absolutely menacing. Within the building lurked an evil presence; it was as if Burke were a prehistoric man in front of a dark cave which smelled of blood and carrion. . . .
He tried the door to the office; it was locked. He knocked.
Somewhere within a presence stirred. Flee while there's still time! Still time! Still time! Don't wait! Don't wait! Too late! Don't wait! Still time!
Tarbert appeared in the doorway—a bloated monstrous Tarbert, a vile malevolent Tarbert. "Hello, Paul," he sneered. "They finally let you out?"
"Yes," said Burke in a voice he could not keep from trembling. "Ralph, am I crazy—or not? Can you see it?"
Tarbert looked at him with the cunning of a hungry shark. He meant to trap Burke, to involve him in misfortune and tragedy.
"It's there."
Burke's breath rasped out through his constricted throat. Margaret's frightened voice came from behind him. "What's there? Tell me, Paul! What is it?"
"The nopal," croaked Burke. "It's sitting on my head, sucking at my mind."
"No!" said Margaret, taking his arm. "Look at me, Paul! Don't believe Tarbert! He's lying! There's nothing there! I can see you, and there's nothing there!"
"I'm not crazy," said Burke. "You can't see it because you've got one too. It won't let you see. It tries to make us believe Ralph is vicious—just as it made you think I was."
Margaret's face sagged in shock and incredulity. "I didn't want to involve you," said Burke, "but since you are, you might as well know what's going on."
"What is a 'nopal'?" whispered Margaret.
"Yes," said Tarbert hollowly, "what is a nopal? I don't know either."
Burke took Margaret's arm, led her into the office. "Sit down." Margaret gingerly took a seat; Tarbert leaned against the counter. "Whatever the nopal is," said Burke, "it's not nice. Evil spirit, familiar, mind-parasite—these are just names; they don't describe the things. But they're able to influence us. Right now, Margaret, they're telling us to hate Tarbert. I never realized how powerful the things are until I turned down Leghorn Road."
Margaret raised her hands to her head. "It's on me now?"
Tarbert nodded. "I can see it. It's not pretty."
Margaret slumped into a chair, hands twisting in her lap. She turned Burke an uncertain white-faced grin. "You're joking, aren't you? Just trying to scare me?"
Burke patted her hand. "I wish I were. But I'm not."
Margaret said, still unbelieving, "But why haven't other people seen them? Why aren't they known to scientists?"
"I'll tell you the whole story."
"Yes," said Tarbert dryly. "I'll be interested to hear it. I know absolutely nothing except that everyone carries a monster riding on their heads."
"Sorry, Ralph," said Burke, grinning. "I imagine it came as something of a shock?"
Tarbert nodded grimly. "You'll never know."
"Well, here's the story . . ."

X
evening had come; the three sat in the workshop, in a pool of light around the denopalizer. On the workbench an electric percolator bubbled.
"It's a cruel situation," said Burke. "Not only for us, but for everyone. I had to have help, Ralph. I had to drag you into it."
Tarbert sat staring at the denopalizer. There was silence in the room, except for the chanted growling sound in Burke's mind. Tarbert still seemed the embodiment of all danger and evil, but Burke, closing his mind to the idea, insisted that Tarbert was his friend and ally—even though he could not look into Tarbert's malevolent countenance.
Burke stirred himself. "You still have a choice. After all, this is not your responsibility—not mine either for that matter. But now that you know what's going on, you can still pull out if you like, and no hard feelings."
Tarbert grinned sadly. "I'm not complaining. Sooner or later I'd have been involved. I'd just as soon be in at the beginning."
"So would I," said Burke with relief. "How long was I in the asylum?"
"About two weeks."
"In about another two weeks the nopal will drop down on you. You'll go to sleep, you'll wake up thinking it was all a terrible nightmare. That's how I felt. You'll have no trouble forgetting it, because the nopal will help you forget."
Tarbert's eyes focused on a spot above Burke's shoulder. He shivered. "With that thing looking at me?" He shook his head. "I don't understand how you can bear hosting it, knowing what it is."
Burke grimaced. "It's doing its best to smother the revulsion. . . . They choke away ideas they don't like—achieve a certain degree of control. They can encourage the hostilities latent in everybody; it's dangerous to be Tauptu in a world of Chitumih."
Margaret stirred uneasily. "I don't understand what you hope to do."
"It's not what we hope to do—it's what we must do. The Xaxans have given us an ultimatum: Clean up our planet, or they'll clean it for us. They have the capabilities; they're ruthless enough."
"I can sympathize with their determination," Tarbert said thoughtfully. "They've apparently suffered a great deal."
"But they're inflicting, or trying to inflict, this same suffering on us!" protested Burke. "I find them callous, harsh, domineering—"
"You saw them under the worst possible circumstances," Tarbert pointed out. "They seemed to treat you as politely as possible. My impulse is to defer judgment on the Xaxans, until we know them better."
"I know them well enough now," growled Burke. "Don't forget, I was witness to—" He stopped short. The nopal presumably were urging him to attack the Xaxans. Tarbert's defense was probably the rational attitude. . . . Still, on the other hand . . . Tarbert interrupted his speculations. "There's a great deal I don't understand," he said. "For instance, they call Earth, Nopalgarth; they want us to purge ourselves of nopal, ostensibly to cure a pest-hole condition. But the universe is very large and there must be many other worlds plagued by nopal. They can't expect to tidy up the entire universe! You can't eradicate mosquitoes by spraying one pool in a swamp."
"According to what I was told," said Burke, "this is precisely their aim. They're conducting an anti-nopal crusade, and we're the first converts. So far as Earth is concerned, it's up to us. We've got a tremendous responsibility —and I don't see how we're going to discharge it."
"But surely," Margaret said uncertainly, "if these things exist, and you told people—"

"Who'd believe us? We can't just start denopalizing each casual passer-by; we'd last about four hours. If we went to some remote island and set up a colony of Tauptu, and if by some chance we escaped persecution and extermination, we'd eventually touch off a Xaxan-type war."
"Then—" Margaret started, but Burke interrupted her: "If we do nothing, the Xaxans will destroy us. They've destroyed millions of Chitumih on Ixax; why should they hesitate to do the same here?"
"We must compose ourselves to quiet reflection," said Tarbert. "I can think of a dozen questions I'd like to explore. Is there any way to expunge these damnable nopal other than the torture machine? Is it possible that the nopal are merely a part of the human organism, such as the so-called soul, or some kind of refracted image of the mental processes? Or possibly of the unconscious mind?"
"If they're part of ourselves," Burke pondered, "Why should they seem so hideous?"
Tarbert laughed. "If I dangled your intestines in front of your face, you'd find them revolting enough."
"True," said Burke. He considered a moment. "In response to your first question: The Xaxans know of no way to purge the Chitumih except by the denopalizer. This of course does not mean that no other way exists. As for nopal being part of the human, organism, they certainly don't act like it. They float around hungrily, they cross to other planets, they act like independent creatures. If some kind of man-nopal symbiosis is involved, it seems all to the benefit of the nopal. So far as I know they confer no advantages upon their host—although I know of no active harm they do either."
"Then why are the Xaxans so all-fired anxious to be rid of them, to cleanse the universe of the nopal?"
"Because they're disgusting, I suppose," said Burke. "That seems reason enough for them."
Margaret shivered. "There must be something wrong with me. ... If these things exist, and you both say they do, I should feel more of this disgust—but I don't. I'm just numb."
"Your nopal clamps down on the proper nerve at the proper time," said Burke.
"This fact," said Tarbert, "would imply that the nopal possesses a considerable intelligence—and sets up a new collection of questions: Does the nopal understand words, or merely feel raw emotion? Apparently it lives upon a single host until the host dies, in which case it has opportunity to learn the language. But, on the other hand, it may not possess that large a memory-bank. Possibly no memory at all."
Margaret said, "If it stays on a person until a person dies, then it's to the nopal's advantage to keep that person alive."
"So it would seem."
"This might account for premonitions of danger, hunches, and things like that."
"Very possibly," said Tarbert. "It's one of the ideas we certainly would want to explore."
There was peremptory knocking at the outside door. Tarbert rose to his feet; Margaret twisted around startled, hand to her mouth.
Tarbert slowly started for the door; Burke stopped him. "Let me go. I'm Chitumih, like everyone else."
He started across the dim workshop, toward the office and the outer door. Halfway he stopped. He looked back. Margaret and Tarbert, in the little island of yellow light, stood immobile, waiting and watching.
He slowly turned, fighting against a fearful reluctance he had come to recognize.
The rap-rap-rap sounded again, a measured ominous sound.
Burke forced his laggard legs into motion, pushed himself through the dark office, past the long counter, to the door.

He looked out through the glass panel, strained to see into the night. The dim half-moon hung behind a tall cypress tree; in a shadow stood a massive dark shape.
Burke slowly opened the door. The figure stalked forward; the flash of headlights from cars passing along Leghorn Road revealed rough gray skin, a jutting ridge of nose like a bent bow, opaque eyes: Pttdu Apiptix, the Xaxan. Behind, in the darkness, more sensed than seen, loomed four other Xaxan shapes. All wore black beetle-shell cloaks and metal helmets with spikes along the ridge.
Apiptix gazed stonily down at Burke. All the hate and fear Burke had originally felt for the Tauptu surged back. He resisted; he thought of his nopal peering at the Xaxans across his shoulders, but to no avail.
Pttdu Apiptix came slowly forward—but now out on the highway a hundred feet away an automobile braked to a halt. A red light began blinking, a search-light swung toward the Electrodyne plant.
Burke jumped forward. "Behind the trees, quick! The Highway Patrol!"
The Xaxans moved into the shadow, to stand like a row of barbaric statues. From the patrol car came the sound of radio voices, then the door opened and two figures alighted.
Heart in throat Burke stepped forward. A flashlight played on his face. "What's the trouble?" he asked.
There was no reply for a moment; nothing but a suspicious scrutiny. Then the trooper's cool voice: "Nothing's the trouble; we're just making a check. Who's inside the plant?"
"Friends."
"You have authority to use this place?"
"Certainly."
"Mind if we take a look around?" They advanced, not caring whether Burke minded or not. Their flash-lights turned here and there, never straying too far from Burke.
"What are you looking for?" Burke asked.
"Nothing in particular. Something's wrong about this place, something fishy going on. There's been trouble here before."
With heart in mouth Burke watched their progress. Twice he started to call a warning; twice his voice caught in his throat. What could he tell them? They were oppressed by the nearness of the Xaxans; there was nervousness in the flick of their lights. Burke could see the shapes under the trees; the lights strayed toward them. . . . Margaret and Tarbert appeared in the doorway. "Who is it?" called Tarbert.
"Highway Patrol," said one of the troopers. "Who are you?"
Tarbert told them. After a moment the patrolmen turned back toward the highway. One of the flashlight beams played into the shadow of the cypress trees. The light hesitated, steadied. The patrolmen gasped. Their revolvers jerked out into their hands. "Come out of there—whoever you are!"
For answer there were two puffs of pink flame, two twinkling pink lines. The patrolmen flared, tumbled back, collapsed like empty sacks.
Burke cried out, stumbled forward, stopped short. Pttdu Apiptix looked at him briefly, then turned to the door. "Let us go in," said the voice-box.
"But these men!" croaked Burke. "You've murdered them!"
"Calm yourself. The corpses will be removed; the automobile also."
Burke looked toward the patrol car, now sounding to the metallic sound of the dispatcher's voice.
"You don't seem to understand what you've done! We can all be arrested, executed . . ." His voice died as he realized the nonsense he was talking. Apiptix, ignoring him, walked into the building with two of his fellows at his heels. The remaining two turned back toward the corpses. Burke shrank back with a crawling skin; Tarbert and Margaret retreated before the stalking gray shapes.

The Xaxans halted at the edge of the pool of light; Burke spoke to Tarbert and Margaret in a bitter voice. "If you harbored any lurking doubts—"
Tarbert nodded shortly. "I've discarded them."
Apiptix approached the denopalizer, examined it without comment. He turned to Burke, "This man"—he indicated Tarbert—"is the single Tauptu on Earth. In the time available you might have organized an entire squadron."
"I've been locked up," said Burke in a surly tone. The hate he felt for Pttdu Apiptix—could it be completely nopal-inspired? "Also, I'm not sure that denopalizing a large number of persons is the best thing to do."
"What else do you propose?"
Tarbert spoke soothingly. "We feel that we must learn more about the nopal. Perhaps there are easier ways to denopalize." He scrutinized the Xaxans with bright interest. "Have you yourselves tried other means?"
Apiptix's mud-colored eyes felt impassively over Tarbert. "We are warriors, not savants. The nopal of Nopalgarth come to Ixax; once a month we burn them away from our minds. They are your pests. You must take immediate steps against them."
Tarbert nodded—with rather too easy an acquiescence, thought Burke resentfully. "We agree that you have cause for impatience."
"We need time!" Burke exclaimed. "Surely you can spare us a month or two!"
"Why do you need time? The denopalizer is ready! Now you must use it!"
"There is such an enormous amount to be learned!" cried Burke. "What are the nopal? No one knows. They seem repulsive, but who knows? Perhaps they even exert a beneficial effect!"
"An amusing speculation." Apiptix appeared anything but amused. "I assure you that the nopal are harmful; they have harmed Ixax by causing a war of a hundred years."
"Are the nopal intelligent?" Burke continued. "Can they communicate with men? These are things we want to know."
Apiptix regarded him with what seemed to be amazement. "From where do you derive these ideas?"
"Sometimes I think the nopal is trying to tell me something."
"To what effect?"
"I'm not sure. When I come close to a Tauptu there's an odd sound in my mind: something like gher, gher, gher."
Apiptix slowly turned his head, as if not trusting himself to look at Burke.
Tarbert said, "It's true that we know very little. Remember, our tradition is to learn first, then act."
"What is nopal-cloth?" asked Burke. "Can it be made from anything beside the nopal? And something else which puzzles me—where did the first piece of nopal-cloth come from? If a single man were accidentally denopalized, it's hard to see how he could have personally fabricated the cloth."
"These are irrelevances," said the Xaxan voice-box.
"Perhaps, perhaps not," said Burke. "They indicate an area of ignorance, which may exist for both of us. For instance, do you know how the first piece of nopal-cloth came into existence, and how?"
The Xaxan stared at him a moment, his beer-colored eyes blank. Burke was unable to read his emotions. Finally the Xaxan said, "The knowledge, if it exists, can not help you destroy the nopal. Proceed then in accordance with your directions."
The voice, though flat and mechanical, still managed to convey sinister overtones. But Burke, summoning all his courage, persisted: "We just can't act blindly. There's too much we don't know. This machine destroys the nopal, but it can't be the best method, or even the best approach to the problem! Look at your own planet: in ruins; your people: almost wiped out! Would you want to inflict the same disaster on Earth? Give us a little time to learn, to experiment, to get a grip on the subject!"

For a moment the Xaxan held to silence. Then the voice-box said, "You Earthmen are over-ripe with subtlety. For us the destruction of nopal is the basic and single issue. Remember, we do not need your help; we can destroy the nopal of Nopalgarth at any time: tonight, tomorrow. Do you wish to know how we will do this, if necessary?" Without waiting for answer he stalked to the table, lifted the scrap of nopal-cloth. "You have used this material, you know its peculiar qualities. You know that it is without mass and inertia, that it responds to telekinesis, that it is almost infinitely extensible, that it is impenetrable to the nopal."
"So we understand."
"If necessary, we are prepared to envelope Earth in a swath of nopal-cloth. We can do this. The nopal will be trapped and as Earth moves they will be pulled away from the brains of their hosts. The brains will hemorrhage and people of Earth will die."
No one spoke. Apiptix continued. "This is a drastic recourse—but we will be tormented no longer. I have explained what must be done. Exterminate your nopal, or we will do so ourselves." He turned away, and with his two comrades, crossed the workshop.
Burke followed, burning with indignation. Trying to keep his voice calm, he said to the tall black-cloaked backs: "You can't expect us to perform miracles! We need time!"
Apiptix did not slow his pace. "You have one week". He and his fellows passed out into the night. Burke and Tarbert followed. The two who had remained outside appeared from the shadow of the cypress trees, but the corpses and the patrol car were nowhere to be seen. Burke tried to speak, but his throat tightened and the words refused to come. As he and Tarbert watched, the Xaxans stood stiffly, then rose into the night, accelerating, blurring, disappearing into the spaces between the stars.
"How in the world do they do that?" Tarbert asked in wonder.
"I don't know." Nauseated and limp Burke sank down upon a step.
"Marvelous!" Tarbert said. "A dynamic people—they make us seem like clams."
Burke gazed at him with suspicion. "Dynamic and murderous," he said sourly. "They've mixed us a pot of trouble. This place will be swarming with police."
"I don't think so," said Tarbert. "The bodies, the car, are gone. It's an unfortunate affair—"
"Especially for the cops."
"You've got nopal trouble," Tarbert remarked, and Burke forced himself to believe that Tarbert was right. He rose to his feet; they returned inside.
Margaret waited in the outer office. "Are they gone?"
Burke nodded curtly. "They're gone."
Margaret shuddered. "I've never been so afraid in my life. It's like swimming and seeing a shark come toward you."
"Your nopal is twisting things," said Burke hollowly. "I can't think straight either." He looked at the denopalizer. "I suppose I should take the treatment." His head suddenly began to throb with pain. "The nopal doesn't think so." He sat down, closed his eyes. The ache slowly diminished.
"I'm not so sure it's a good idea," said Tarbert. "You'd better keep your nopal for awhile. One of us has to enlist recruits for the squadron—as the Xaxan puts it."
"Then what?" asked Burke in a muffled voice. "Tommy-guns? Molotov cocktails? Bombs? Who do we fight first?"
"It's so brutal and senseless!" Margaret protested fiercely.
Burke agreed. "It's a brutal situation—and we can't do much about it. They allow us no freedom of action."
"They've spent a century fighting these things," Tarbert argued. "They probably know all there is to know about the nopal."

Burke sat up in outrage. "Good heavens no! They admit they know nothing! They're pushing us, trying to keep us off-balance. Why? A few days more or less—what's the difference? There's something peculiar going on!"
"Nopal-talk. The Xaxans are harsh, but they seem honest. Apparently they aren't as ruthless as the nopal would have you think. Otherwise they'd denopalize Earth at once without giving us the chance to do it ourselves."
Burke tried to order his thoughts.
"Either that," he said presently, "or they have another reason for wanting Earth denopalized but populated."
"What reason could they have?" asked Margaret.
Tarbert shook his head skeptically. "We're becoming overripe again, as the Xaxans would say."
"They allow us no time whatever for research," said Burke. "Personally I don't want to embark on a project as big as this without studying it. It's only reasonable that they give us a few months."
"We've got a week," said Tarbert.
"A week!" snarled Burke. He kicked the denopalizer. "If they'd allow us to work up something different, something easy and painless, we'd all be better off." He poured a cup of coffee, tasted it, spat in disgust. "It's been boiling."
"I'll make fresh," Margaret said hurriedly.
"We've got a week," said Tarbert, pacing with hands behind his back. "A week to conceive, explore and develop a new science."
"Nothing to it," said Burke. "It's only necessary to fix on a method of approach, invent tools and research techniques, work up nomenclatures. Then it's duck soup. We merely concentrate on the specific application: the swift denopalization of Nopalgarth. After sorting through and testing our ideas, we can take the rest of the week off."
"Well, to work," Tarbert said dryly. "Our starting point is the fact that the nopal exist. I'm watching your private nopal, and I can see that it doesn't like me."
Burke squirmed fretfully, aware—or at least imagining himself aware—of the entity on his neck.
"Don't remind us," said Margaret, returning with the percolator. "It's bad enough simply knowing."
"Sorry," said Tarbert. "So we start with the nopal, creatures completely outside our old scheme of things. The simple fact of their existence is meaningful. What are they? Ghosts? Spirits? Demons?"
"What difference does it make?" growled Burke. "Classifying them doesn't explain them."
Tarbert paid him no heed. "Whatever they are, they're built of stuff foreign to us: a new kind of matter, only semi-visible, impalpable, without mass or inertia. They seem to draw nourishment from the mind, from the process of thought, and their dead bodies respond to telekinesis, a most suggestive situation."
"It suggests that thought is a process rather more substantial than we've heretofore believed," said Burke. "Or perhaps I should say that there seem to be substantial processes going on, which relate to thought in some manner we can't yet define."
"Telepathy, clairvoyance, and the like—the so-called psionic phenomena—indicate the same, of course," mused Tarbert. "It's possible that nopal-stuff is the operative material. When something—a thought or a vivid impression—passes from one mind to another, the minds are physically linked —somehow, in some degree. Action at a distance can't be allowed. In order to know the nopal, we might well concern ourselves with thought."

Burke wearily shook his head. "We know no more about thought than we do about the nopal. Even less. Encephalographs record a by-product of thought. Surgeons report that certain parts of the brain are associated with certain kinds of thought. We suspect that telepathy occurs instantaneously, if no faster—"
"How could anything be faster than instantaneous?" Margaret inquired.
"It could arrive before it started. In which case it's called precognition."
"Oh."
"In any event it seems that thought is a different stuff from our usual matter, that it obeys different laws, acts through a different medium, in a different dimension-set, in short, works through a different space—implying a different universe."
Tarbert frowned. "You're getting a little carried away; you're using the word 'thought' rather too easily. After all, what is 'thought? So far as we know, it's a word to describe a complex of electrical and chemical processes in our brains, these more elaborate, but intrinsically no more mysterious, than the operation of a computer. With all the good will and predisposition in the world, I can't see how 'thought' can work metaphysical miracles."
"In this case," said Burke, somewhat tartly, "what do you suggest?"
"Just for a starter, some recent speculations in the field of nuclear physics. You're naturally aware how the neutrino was discovered: more energy went into a reaction then came out of it, suggesting that an undiscovered particle was at work.
"Well, new, rather more subtle, discrepancies have shown themselves: Parities and indexes of strangeness don't come out quite right, and it seems that there's a new and unsuspected 'weak' force at work."
"Where does all this take us?" demanded Burke, then forced himself to erase his exasperated frown and replace it with a somewhat pallid smile. "Sorry."
Tarbert made an unworried gesture. "I'm watching your nopal. . . . Where does all this take us? We know of two strong forces: nuclear-binding energy, electro-magnetic fields; and—if we ignore the beta decay force—one weak force: gravity. The fourth force is far weaker than gravity, even less perceptible than the neutrino. The implications seem to be—or at least, may be—that the universe has a shadow counterpart, completely congruent, based upon this fourth force. It's still all one universe naturally and there's no question of new dimensions or anything bizarre. Just that the material universe has at least another aspect composed of a substance, or field, or structure—whatever you want to call it—invisible to our senses and sensor mechanisms."
"I've read something of this in one of the journals," said Burke. "At the time I didn't pay too much attention. . . . I'm sure you're on the right track. This weak-force universe, or para-cosmos, must be the environment of the nopal, as well as the domain of psionic phenomena."
Margaret was moved to exclaim. "But you insisted that this fourth-force 'para-cosmos' is undetectable! If telepathy isn't detectable, how do we know it exists?"
Tarbert laughed. "A lot of people say it doesn't exist. They haven't seen the nopal." He turned a wry glance at the space over Burke's and Margaret's heads. "The fact is that the para-cosmos is not quite undetectable. If it were, the discrepancies by which the fourth force has been discovered would never have been noticed."
"Assuming all this," said Burke, "and of course we've got to assume something, it appears that the fourth force, if sufficiently concentrated, can influence matter. More accurately, the fourth force influences matter, but only when the force is intensely concentrated do we notice the effect."
Margaret was puzzled. "Telepathy is a projection or a beam of this 'fourth force'?"
"No," said Tarbert. "I wouldn't think so. Remember, our brains can't generate the 'fourth force.' I don't think we need to stray too far from conventional physics to explain psionic events—once we assume the existence of an analogue universe, congruent to our own."

"I still don't see it," said Margaret. "And isn't telepathy supposed to be instantaneous? If the analogue world is exactly congruent to our own, why shouldn't events take place at the same speed?"
"Well—" Tarbert considered a few minutes. "Here's some more hypothesis—or I'll even call it 'induction.' What we know of telepathy and the nopal suggests that the analogue particles enjoy considerably greater freedom than our own —balloons compared to bricks. They're constructed of very weak fields, and also, much more importantly, aren't constrained to rigidity by the strong fields. In other words, the analogue world is topologically congruent to our own but not dimensionally. In fact, dimensions have no real meaning."
"If so, 'velocity' is also a meaningless word, and 'time' as well," said Burke. "This may give us a hint as to the theory of the Xaxan space-ships. Do you think it's possible that somehow they enter the analogue universe?" He held up his hand as Tarbert started to speak. "I know—they're already in the analogue universe. We mustn't confuse ourselves with fourth-dimensional concepts."
"Correct," said Tarbert. "But back to the linkage between the universes. I like the balloon-brick image. Each balloon is tied to a brick. The bricks can disturb the balloons, but vice-versa, not so easily. Let's consider how it works in the case of telepathy. Currents in my mind generate a corresponding flow in the para-cosmos analogue of my mind— my shadow-mind, so to speak. This is a case of the bricks jerking the balloons. By some unknown mechanism, maybe by my analogue self creating analogue vibrations which are interpreted by another analogue personality, the balloons jerk the bricks; the neural currents are transferred back to the receiving brain. If conditions are right."
"These 'conditions,' " said Burke sourly, "may very well be the nopal."
"True. The nopal apparently are creatures of the para-cosmos, constructed of balloon-stuff, and for some reason viable in either of the universes."
The coffee had percolated; Margaret poured. "I wonder," she asked, "if possibly the nopal have no existence in this universe whatever?"
Tarbert raised his eyebrows in pained protest—a demonstration Burke thought rather exaggerated. "But I can see them!"
"Perhaps you only think you do. Suppose the nopal existed only in the other cosmos, and preyed only on the analogues? You see them by clairvoyance, or rather, your analogue sees them—and it's so clear and vivid you think the nopal are real material objects."
"But my dear young lady—"
Burke interrupted. "It's quite sensible. I saw the nopal too; I know how real they appear. But they neither reflect nor radiate light. If they did, they'd appear on photographs. I don't believe they do have any base-world reality whatever."
Tarbert shrugged. "If they can prevent us from recognizing them in the natural state, they could do the same for photographs."
"In many cases photographs are scanned by mechanical means. Irregularities could not help but show up."
Tarbert glanced at the air beside Burke's shoulder. "If you're right, why aren't the Xaxans aware of the situation?"
"They admit they know nothing of the nopal."
"They could hardly ignore something so basic," argued Tarbert. "The Xaxans are scarcely naive."
"I'm not so sure. Tonight Pttdu Apiptix acted unreasonably. Unless . . ."
"Unless what?" asked Tarbert with, what Burke considered, undue sharpness.
"Unless the Xaxans have some sort of ulterior motive. That's what I was about to say. I know it's ridiculous. I saw their planet; I know what they've suffered."
"There's certainly a great deal we don't understand," Tarbert admitted.
"I'd breath a lot easier if a nopal weren't actually resting on my actual neck," said Margaret. "If it's only harassing my analogue—"
Tarbert leaned quickly forward. "Your analogue is part of you, don't forget. You don't see your liver, but it's there and functioning. Just so your analogue."
"You agree that Margaret may be right?" asked Burke cautiously. "That the nopal actually is confined to the para-cosmos?"
"Well, it's as good a guess as any other," said Tarbert grudgingly. "I can think of two arguments counter. First the nopal-cloth, which I move with these, my own personal hands. Second, the control exerted by the nopal over our emotions and perceptions."
Burke jumped to his feet, paced back and forth. "The nopal might exert its influence through the analogue, so that when I think I'm touching nopal-cloth I'm only grasping air, that it's really the analogue who does the work—in fact, this is implication of the previous theory."
"In this case," said Tarbert, "Why can't I visualize myself chopping up nopal with an imaginary axe?"
Burke felt a twinge of alarm. "No reason at all, I suppose."
Tarbert appraised the wisp of nopal-cloth. "No mass, no inertia—at least not in the base universe. If my telekinetic powers are up to it I should be able to manipulate this nopal-stuff." The film rose limply into the air. Burke watched in revulsion. Disgusting stuff. It made him think of corpses, corruption, death.
Tarbert turned his head sharply. "Are you resisting me?"
Tarbert's arrogance, never his most endearing quality, was becoming intolerable, thought Burke. He started to say as much, then noting the malicious amusement in Tarbert's eyes, clamped his mouth shut. He glanced at Margaret, to find her watching Tarbert with a loathing equal to his own. The two of them perhaps might be able to ...
Burke caught himself up short, appalled by the direction of his thoughts. The nopal had infected him, this was only too clear. On the other hand—why should not a man have an idea of his own? Tarbert had become twisted and malevolent; sheer dispassionate judgment could discern as much. Tarbert was tool to the alien creatures, not Burke! Tarbert and the Xaxans—enemies to Earth! Burke must counter them, or everyone would be destroyed. . . . Burke watched vigilantly as Tarbert concentrated on the nopal-cloth. The smoky wisp shifted, changed shape slowly, reluctantly.
Tarbert laughed rather nervously. "It's hard work. In the para-cosmos the stuff is probably fairly rigid. . . . Care to try?"
"No," said Burke in a throaty voice.
"Nopal-trouble?"
Burke wondered why Tarbert jeered so offensively.
Tarbert said, "Your nopal is excited. Its plumes are fluttering and flickering. . . ."
"Why pick on the nopal?" Burke heard himself saying. "Other things are happening."
Tarbert gave him a sidelong glance. "That's a curious thing to say."
Burke halted in his pacing, rubbed his face. "Yes. Now that you mention it."
"Did the nopal put the words in your mouth?"
"No . . ." But Burke was not completely certain. "I had an intuition, something of the sort. The nopal probably was responsible. It gave me a quick glimpse of—something."
" 'Something'? Such as?"
"I don't know. I don't even remember it."
"Hmmph," said Tarbert. He turned his attention back once more to the wad of nopal-cloth, causing it to rise, fall, twist and spin. Suddenly he sent it darting twenty feet across the room, then gave a hideous laugh. "I've just battered hell out of a nopal." He looked speculatively at Burke, turned his gaze over Burke's head.
Burke found himself on his feet, lurching slowly toward Tarbert. In his brain sounded the guttural now-familiar vocable: gher gher gher . . .

Tarbert drew back. "Don't let the thing dominate you, Paul. It's afraid, it's desperate."
Burke halted.
"If you don't beat it we've lost our fight—before we've even started." Tarbert looked from Burke to Margaret. "Neither of you hate me. Your nopal fear me."
Burke looked at Margaret. Her face was tight and strained. Her eyes met his.
Burke took a deep breath. "You're right," he said huskily. "You've got to be right." He returned to his seat. "And I've got to restrain myself. Your playing with that nopal-stuff does something to me, you'll never know. . .."
"Don't forget that I was 'Chitumih' myself once," said Tarbert, "and I had to put up with you."
"You're hardly tactful."
Tarbert grinned, turned his attention back to the wad of nopal-stuff. "This is an interesting process. If I work hard I can wad it up. . . . I suppose that given enough time I could wipe out much of the nopal population. . . ."
Burke, seating himself, watched Tarbert with a stony gaze. After a moment he forced himself to relax. With the easing of taut muscles came the knowledge that he was very tired.
Tarbert said thoughtfully, "Now I'll try something else. I form two pads of nopal-stuff, I catch a nopal between; I squeeze. . . . There's resistance; then the thing collapses. Like cracking a walnut."
Burke winced. Tarbert looked at him with interest. "Certainly you don't feel that?"
"Not directly."
Tarbert mused. "It's nothing to do with your own nopal."
"No," said Burke drearily. "It's just a twinge—induced fear—" He lacked both interest and energy to continue. "What time is it?"
"Almost three o'clock," said Margaret. She looked longingly toward the door. Like Burke she felt limp and drawn. How wonderful to be home in bed, indifferent to the nopal and all these strange problems. . . .
Tarbert, absorbed in his game of nopal-smashing, seemed fresh as the morning sun. A nauseous business, thought Burke. Tarbert was like an unpleasant urchin catching flies .... Tarbert glanced at him, frowning, and Burke sat up in his chair, aware of a new tension. From a state of listless disapproval, he had begun to take a gradually more active interest in the game, and now found himself resisting Tarbert's manipulations of the nopal-stuff with all his will. He was committed; hostility became overt between the two men. Beads of sweat started from Burke's forehead; his eyeballs thrust from their sockets. Tarbert sat rigid, face pinched and white as a skull. The nopal-stuff quivered; wisps and torn fragments wavered back and forth, into and away from the parent substance.
An idea came to Burke's mind, grew into conviction: this was more than an idle contest—much more! Happiness, peace, survival—all, everything, depended on the outcome. Holding the nopal-stuff rigid was not enough; he must wield it, slash at Tarbert, cut the vital cord, the umbilicus. . . . The nopal-stuff streamed and shifted to Burke's fervor, edged toward Tarbert. Something new occurred, something unforeseen and frightening. Tarbert ballooned with mental energy. The nopal-stuff was whisked from Burke's mental-grip, flung far out of his control.
The game was at an end; likewise the contest of wills. Burke and Tarbert looked at each other, startled and bemused. "What happened?" asked Burke in a strained voice.
"I don't know." Tarbert rubbed his forehead. "Something came over me. ... I felt like a giant—irresistible." He laughed wanly. "It was quite a sensation. . . ."
There was silence for a moment. Then Burke said in a shaky voice, "Ralph, I can't trust myself; I've got to get rid of this nopal. Before it makes me do something—bad."

Tarbert considered for another long minute. "Perhaps you're right," he said at last. "If we're constantly at odd's-ends, we'll accomplish nothing." He rose slowly to his feet. "Very well, I'll denopalize you. If Margaret can put up with two fiends incarnate instead of just one." He chuckled feebly.
"I can stand it. If it's necessary." And she muttered, "I suppose it is. ... I hope it is. In fact, I know it must be."
"Let's get it over with." Burke stood up, forced himself toward the denopalizer. The rage and reluctance of the nopal pressed at him, sapped the strength off his muscles.
Tarbert looked sourly at Margaret. "You'd better go."
She shook her head. "Please let me stay."
Tarbert shrugged; Burke was too weary to insist. A step toward the denopalizer, another step, a third—it was like walking through deep mud. The nopal's efforts became frantic; lights and colors played across Burke's field of vision; the grating sound was an audible croak: "Gher—gher— gher..."
Burke stopped to rest. The colors crawling before his eyes took on queer forms. If only he could see; if only he would look. . . .
Tarbert, watching him, frowned. "What's the trouble?"
"The nopal is trying to show me something—or letting me see. . . . I'm not looking correctly." He closed his eyes, hoping to discipline the black smears, the golden whorls, the skeins of fibrous blue and green.
Tarbert's voice came plangent through the darkness. He seemed irritated. "Come, Paul—let's get it over with."
"Wait," said Burke. "I'm getting the hang of it. The trick is to look through your mental eyes—your mind's-eye. The eyes of your analogue. Then you see . . ." His voice dwindled into a soft sigh, as the flickerings steadied and for a brief moment composed themselves. He was looking across a wild strange panorama, composed of superimposed black and gold landscapes, and like a scene through a stereoscopic viewer it was both clear and distorted, familiar and fantastic. He saw stars and space, black mountains, green and blue flames, comets, watery sea-bottoms, molecules moving, networks of nerves. If he chose to use his analogue hand, he could reach to every point of this multi-phase region, and still it extended across a greater and more complicated space than all the familiar universe.
He saw the nopal, much more substantial than the wisps of film and froth he had glimpsed before. But here in this analogue cosmos they were unimportant, secondary to a colossal shape crouching in an indefinable mid-region, a black corpulence in which floated half-unseen a golden nucleus, like the moon behind clouds. From the dark shape issued a billion flagellae, white as new corn-silk, streaming and waving, reaching into every corner of this complicated space. At the end of certain strands Burke sensed dangling shapes, like puppets on a string, like plump rotten fruit, like hanged men on a rope. The fibrils reached near and far. One came into Electrodyne Engineering, where it clamped to Tarbert's head with a sensitive palp like a rubber suction-cup. Along the strand, nopal clustered; they seemed to be gnawing, rasping. Burke understood that when they gnawed sufficiently the fibril would draw back in frustration, leaving a naked unprotected scalp. Directly over his own head wavered another of the fibrils, ending in an empty sucker-palp. Burke could follow back along the length of the fibril, across distances which were at once as far as the end of the universe, and as close as the wall; he could look into the focus of the gher. The glazed yellow nucleus studied him with so avid, so intent and intelligent a malice that Burke mumbled and muttered.
"What's the trouble, Paul?" came Margaret's anxious voice. He could see her, too: clearly and recognizably Margaret, although her image wavered as if caught in a column of heated air. Now he could see many people; if he wanted, he could talk to any of them. They were as far as China but as close as the tip of his nose. "Are you all right?" spoke the vision of Margaret, in wordless words, in soundless sounds.
Burke opened his eyes. "Yes," he said. "I'm all right."
The vision had lasted a second, two seconds. Burke looked at Tarbert; they stared eye to eye. The gher controlled Tarbert; it controlled the Xaxans; it had controlled Burke himself until the nopal had gnawed away the fibril. The nopal—fussy, limited little parasites!—striving to survive they had betrayed their great enemy!
"Let's get started," said Tarbert.
Burke said cautiously, "I want to think things over a bit."
Tarbert studied him with a bland, blind look. Cold eddies played along Burke's nerves. The gher was instructing its agent. "Did you hear me?" asked Burke.
"Yes," said Tarbert in a syrup-sweet voice. "I heard you." His eyes—to Burke's imagination—shone with a dull golden shine.

XI
burke rose to his feet and walked, a slow step at a time. Two feet from Tarbert he halted, looking into the face of his friend, trying to achieve objectivity. He failed; he felt horror and hate. How much derived from the nopal? Compensate! He told himself. Over-compensate!
"Ralph," he said in as even a voice as he could manage, "we've got to make quite an effort. I know what the gher is. It rides you just like the nopal rides me."
Tarbert shook his head, grinning like a haggard gray fox. "That's your nopal talking."
"And the gher talks through you."
"I don't believe that." Tarbert himself was striving for objectivity. "Paul—you know what the nopal are. Don't underestimate their cunning!"
Burke laughed sadly. "This is like an argument between a Christian and a Moslem: each thinks the other a misguided heathen. Neither of us can convince the other. So— what are we going to do?"
"I think it's important that you be denopalized."
"For the benefit of the gher? No."
"Then what do you suggest?"
"I don't know. This business becomes ever more complicated. For the moment we can't trust ourselves to think straight—let alone trust each other. We've got to straighten things out."
"I agree completely." Tarbert seemed to relax, to ponder. Almost absentmindedly he toyed with the floating wad of nopal-stuff, kneading it with vast authority, forming it into a pillow of apparent density.
Careful!
"Let's see if we can find our lowest common denominator of agreement," said Tarbert. "I feel that the denopalization of Earth is our prime concern."
Burke shook his head somberly. "Our basic duty is—"
"This." Tarbert acted. The nopal-stuff lurched, spun through the air, thrust down over Burke's head. The spines of the nopal momentarily supported, distended the substance; then they crumpled. The pressure on Burke's head was palpable; he felt as if he were smothering. With his fingers he tried to claw the stuff away; with his mind he tried to banish it, but Tarbert had the advantage of impetus. The nopal suddenly shivered, collapsed like an egg-shell. Burke felt jolting shock, as if a hammer had tapped his exposed brain. His vision swarmed with blazing blue lightning-flashes, bursts of glowing yellow.
The pressure ceased; the lights faded. In spite of his rage at Tarbert's treachery, in spite of the pain and dazzle, he recognized a new state of well-being. It was as if a sodden head-cold had been cured; as if, while choking, his lungs had opened to fresh air.
He could afford no time for introspection. The nopal was crushed. All to the good; what of the gher? He focused his mental gaze. To all sides floated the nopal, fluttering their plumes like outraged harridans. The arm of the gher hung overhead. Why did it hesitate? Why was its motion so uncertain? It hovered closer, drifted gingerly down; Burke ducked, reached for the tatters of the crushed nopal, at the collapsed mantle of nopal-stuff, pulling it over his head. The sucker slid down again, feeling, exploring. Burke dodged away once more, smoothing the protective mantle about his skull. Margaret and Tarbert watched in wonder. The nopal nearby jerked and quivered in excitement. Far away loomed the gher—half the distance of the universe?—bulking like a mountain into the night sky.

Burke became furious. He was free; why should he submit to the gher? He seized a fragment of nopal-stuff in his hand, in the hand of his analogue, whirled it up, beat at the sucker, at the fibril. The sucker curled back like the lip of a snarling dog, swayed, withdrew in annoyance.
Burke laughed wildly. "Don't like that, eh? I've just started!"
"Paul," cried Margaret. "Paul!"
"Just a minute," said Burke. He slashed at the sucker— again, again. There was restraining friction. Burke looked around. At his side stood Ralph Tarbert, clutching at the nopal-matter, straining against Burke's efforts. Burke pulled and heaved, to no avail. . . . Was this Tarbert, after all? It looked like him, yet with a curious distortion. . . . Burke blinked. He was wrong. Tarbert sat half-sprawled in his chair, eyes half-closed. . . . Two Tarberts? No! One of them naturally would be his analogue, acting at the bidding of Tarbert's mind. But how did the analogue detach itself? Was it an entity in itself? Or was the separation only apparent, the result of para-cosmos distortion? Burke peered into the haggard face. "Ralph, do you hear me?"
Tarbert moved, straightened up in his chair. "Yes, I hear you."
"Do you believe what I told you about the gher?"
There was a moment's hesitation. Then Tarbert gave a great sad sigh. "Yes. I believe you. There was something— I don't know what—controlling me."
Burke studied him a moment. "I can fight the gher, if you won't resist me."
Tarbert gave a weak laugh. "Then what? The nopal again? Which is worse?"
"The gher."
Tarbert closed his eyes. "I can't guarantee anything. I'll try."
Burke looked back into the para-cosmos. Far away—or was it close at hand?—the orb of the gher flickered with caution and alarm. Burke took a fragment of nopal-stuff, tried to form it, but in the hands of his analogue the stuff was tough and refractory. By dint of great effort Burke worked the material, and finally achieved a lumpy bar. He confronted the far brooding form, feeling trivial, an infinitesimal David before a colossal Goliath. To attack, he must wield the bar across an immense gap. . . . Burke blinked. Was the distance so far? Was the gher, after all, so enormous? The perspectives twinkled and shifted, like the angles in a visual puzzle—and abruptly the gher seemed to hang no more than a hundred feet away—or perhaps as close as ten feet. . . . Burke jerked back startled. He hefted the bar, swung it sidewise. It struck the black hulk and collapsed as if it were foam. The gher—a hundred miles, a thousand miles distant—ignored Burke, the indifference more insulting than hostility.
Burke glowered toward the monstrous thing. The internal orb swam and bulged, the myriad capillaries glistened with silken luster. He shifted his gaze, traced the fibril running to Tarbert's head. He reached out, seized it, pulled hard. There was resistance, then the fibril parted, the sucker fell loose, twitching and squirming. The creature was not absolutely invulnerable; it could be hurt! Nopal settled swiftly for Tarbert's unprotected scalp; Burke could see the mental emanations blooming like a luminous flower. One enormous nopal reached the prize first—but Burke interposed a fragment of nopal-stuff, encasing Tarbert's head. The nopal drew back frustrated, the orbs solemn and minatory. The gher abandoned its placidity; the golden orb rolled and wallowed furiously.
Burke turned his attention to Margaret. Her nopal glared back at him, aware of its danger. Tarbert raised his hand to deter Burke from hasty action. "Better wait—we might need someone to front for us. She's still a Chitumih. . . ."
Margaret sighed; her nopal calmed itself. Burke looked back to the gher, now remote, at the end of the universe, swimming in a cool black flux.
Burke poured himself a cup of coffee, settled into a chair with a sigh of fatigue. He watched Tarbert who was staring into mid-air with a rapt expression. "Do you see it?"
"Yes. So that's the gher."
Margaret shuddered. "What is it?"

Burke described the gher and the bizarre environment in which it lived. "The nopal are its enemies. The nopal are semi-intelligent; the gher displays what I would call an evil wisdom. As far as we're concerned one is no better than the other. The nopal is more active. It seems that after gnawing about a month it can break the gher's fibril, and displace the gher's sucker-pad. I tried chopping at the gher, unsuccessfully. It's the toughest object there— presumably because of the energy available to it."
Margaret, sipping coffee, looked critically at Burke over her cup. "I though you couldn't be denopalized except by that machine. . . . But now—"
"Now that I lack my nopal, you hate me again."
"Not so much," said Margaret. "I can control it. But how—"
"The Xaxans were quite explicit. They told me that the nopal could not be pulled loose from the brain. They never tried smashing the nopal into a mat. The gher wouldn't allow it. Tarbert was too quick for the gher."
"An accident, pure and simple," said Tarbert modestly.
"Why aren't the Xaxans aware of the gher?" Margaret demanded. "Why didn't the nopal let them see it, or show it to them, as they did with you?"
Burke shook his head. "I don't know. Possibly because the Xaxans aren't susceptible to visual stimuli. They don't see in the sense that we do. They form three-dimensional models inside their brains, which they interpret by means of tactile nerve-endings. The nopal, remember, are flimsy creatures—stuff of the para-cosmos, balloons compared to the bricks we're made of. They can excite relatively feeble neural currents in our minds—enough for visual stimulation, but perhaps they can't manipulate the more massive mental processes of the Xaxans. The gher made a mistake when it sent the Xaxans to organize Earth. It ignored our susceptibility to hallucination and visions. So we're in luck—temporarily. For the first round at least, neither nopal nor gher have won. They've only alerted us."
"The second round is coming up," said Tarbert. "Three people won't be hard to kill."
Burke rose uneasily to his feet. "If only there were more of us." He scowled toward the denopalizing machine. "At least we can ignore that brutal thing."
Margaret looked anxiously toward the door. "We should leave here—go someplace where the Xaxans can't find us."
"I'd like to hide," said Burke. "But where? We can't dodge the gher."
Tarbert looked off into space. "It's an ugly thing," he said presently.
"What can it do?" quavered Margaret.
"It can't hurt us from the para-cosmos," said Burke. "It's tough, but it's still no harder than thought."
"There's an awful lot of it," said Tarbert. "A cubic mile? A cubic light-year?"
"Maybe just a cubic foot," said Burke. "Maybe a cubic inch. Physical measurements don't mean anything; it's how much energy it's able to turn against us. If for example—"
Margaret jerked around, held up her hand. "Shhh."
Burke and Tarbert looked at her in surprise. They listened, but heard nothing.
"What did you hear?" Burke asked.
"Nothing. I just feel cold all over. ... I think the Xaxans are coming back."
Neither Burke nor Tarbert thought to question the accuracy of her feelings. "Let's go out the back way," said Burke. "They won't be here for any good purpose."
"In fact," said Tarbert, "they're here to kill us."
They crossed the workshop to the sliding doors which opened into the dark warehouse, stepped through. Burke slid the doors together, leaving a half-inch crack.
Tarbert muttered, "I'll check outside. They might be watching the back." He disappeared into the dark. Burke and Margaret heard his footsteps echoing stealthily across the concrete floor.

Burke put his eye to the crack. Across the shop, the door into the office eased open. Burke saw a flicker of movement, then the room exploded with soundless purple glare.
Burke staggered away from the crack. A purple flickering light, thick as smoke, followed him.
Margaret grasped his arm, supported him. "Paul! Are you—?"
Burke rubbed his forehead. "I can't see," he said in a muffled voice. "Otherwise I'm all right." He tried to look with the vision of his analogue—which might or might not be similarly affected. Straining into the dark, the scene began to come clear to him: the building, the screen of cypress trees, the ominous shapes of four Xaxans. Two stood in the office; one patrolled the front of the building; one circled around toward the warehouse entrance. From each, a pale fiber led to the gher. Tarbert was at the outer door. If he opened it, he would meet the approaching Xaxan.
"Ralph!" hissed Burke.
"I see him," Tarbert's voice came back. "I've thrown the bolt on the door."
With hammering pulses they heard the quiet sound of the outside latch being tried.
"Perhaps they'll go away," whispered Margaret.
"Small chance of that," said Burke.
"But they'll—"
"They'll kill us, if we let them."
Margaret was breathlessly silent a moment. Then she asked, "How can we stop them?"
"We can break their connection to the gher. Try to, at least. That might dissuade them."
The door creaked.
"They know we're here," said Burke. He stared into nothingness, willing himself to see through his analogue's eyes.
Two Xaxans had entered the workshop. One of these, Pttdu Apiptix, took a slow stride toward the sliding doors— another and another. Staring into the para-cosmos, Burke traced the fibril which led to the gher. He reached forth his analogue hand, seized it, pulled. This time the struggle was intense. The gher by some means stiffened the fiber, and caused it to vibrate, and Burke felt a pang of vague pain as he heaved and pulled. Apiptix chattered with rage, clutched at his head. The fibril broke, the palp slipped away. Down upon the crested head plumped a nopal, plumes fluttering complacently, and Apiptix groaned in dismay.
The back door to the warehouse jarred. Burke turned, to see Tarbert twisting at another fibril. It broke, a second Xaxan lost his link to the gher.
Burke looked back through the crack into the workshop. Apiptix stood rigid, as if stunned. Two of his fellows entered the room, to stare at him. Burke reached forth with his analogue hands, broke one of the fibrils. Tarbert broke the other. The Xaxans came to a rigid halt, as if stunned. Nopal immediately settled on their heads.
Burke, standing with eye to crack, watched in a turmoil of indecision. If the Xaxans had been acting under compulsion of the gher, all might be well. On the other hand, they were now Chitumih and he Tauptu—an equal incentive to murder.
Margaret tugged at Burke's arm. "Let me go out there."
"No," whispered Burke. "We can't trust them."
"The nopal are back on them again, aren't they?"
"Yes."
"I can feel the difference. They won't bother me." Without waiting for Burke's reply she pushed open the door, entered the shop.
The Xaxans stood motionless. Margaret approached, confronted them. "Why did you try to kill us?"
The chest-plates of Pttdu Apiptix clicked, stuttered; the voice-box spoke. "You did not obey our orders."

Margaret shook her head. "That's not true! You told us we could have a week to make our arrangements. It's been only a few hours!"
Pttdu Apiptix seemed discomfited, uncertain. He turned toward the office door. "We will go."
"Do you still intend to harm us?" asked Margaret.
Pttdu Apiptix made no direct reply. "I have become Chitumih. All of us are Chitumih. We must be purged."
Burke left the shelter of the warehouse and rather sheepishly came forward. The nopal newly established on Pttdu Apiptix ruffled its plumes furiously. Apiptix jerkily raised his hand; Burke moved more quickly. He seized the wad of nopal-stuff, thrust it down upon the Xaxan. The nopal was smashed, felted down over the crested gray head. Pttdu Apiptix staggered to the jolt of pain, peered drunkenly toward Burke.
"You are no longer Chitumih," said Burke. "You are no longer a creature of the gher."
"The 'gher'?" inquired the voice-box, ridiculously toneless. "I do not know of the 'gher'."
"Look into the other world," said Burke. "The" world of thought. You will see the gher."
Pttdu Apiptix gazed at him blankly. Burke amplified his instructions. The Xaxan shuttered his eyes, lizard-gray membranes folding across the dull surfaces. "I see strange shapes. They make no solidity. I can feel a pressure. . . ."
There was a moment of silence. Tarbert entered the shop.
The Xaxan's chest-plates suddenly rattled like hail. The voice-box gurgled, stammered, apparently balked by concepts not included in its index. It spoke. "I see the gher. I see the nopal. They live in a land my brain cannot form .... What are these things?"
Burke slumped down into a chair. He poured himself some coffee, emptying the pot. Margaret automatically went to make fresh coffee. Burke drew a deep breath, explained what little he knew of the para-cosmos, including the area of his and Tarbert's theorizing. "The gher is to the Tauptu what the nopal is to the Chitumih. A hundred and twenty years ago, the gher was able to dislodge the nopal from one Xaxan—"
"The first Tauptu."
"The first Tauptu on Ixax. The gher provided the original sample of nopal-stuff—where else could it come from? The Tauptu were to become warriors for the gher, crusading from planet to planet. The gher sent you here to Earth, to expel the nopal, to lay bare the brains of Earth. Eventually the nopal would be eradicated; the gher would be supreme in the para-cosmos. So the gher hoped."
"So the gher still hopes," said Tarbert. "There's very little to prevent it."
"I must return to Ixax," said Pttdu Apiptix. Even the mechanical delivery of the voice-box could not conceal his desolation of spirit.
Burke chuckled morosely. "You'll be seized and penned up as soon as you show your face."
The Xaxan's chest-plates rang with an incisive angry clicking. "I wear the six-prong helmet. I am Space Lord."
"That makes no difference to the gher."
"Must we fight another war then? Must there be a new division into Tauptu and Chitumih?"
Burke shrugged. "More likely either the nopal or the gher will kill us before we can start any such war."
"Let us kill them first."
Burke laughed shortly. "I wish I knew how."
Tarbert started to speak, then relapsed into silence. He sat with eyes half-closed, attention fixed on the other world. Burke asked, "Well, Ralph, what do you see?"
"The gher. It seems to be agitated."
Burke channeled his own gaze into the para-cosmos. The gher hung in the analogue of the night sky, among great blurred star-spheres. It shivered and jerked; the central orb rolled like a pumpkin in a dark lake. Burke watched in fascination, and seemed to see in the background a wild remote landscape.
"Everything in the para-cosmos has a counterpart in the basic universe," mused Tarbert in a detached voice. "What object or creature in our universe is the counterpart of the gher?"
Burke jerked his gaze away from the gher, stared at Tarbert. "If we could locate the gher's counterpart—"
"Precisely."
Fatigue forgotten, Burke hitched himself forward in his chair. "If it's true for the gher, it should be equally true for the nopal."
"Precisely," said Tarbert a second time.
Apiptix came forward. "Denopalize my men. I wish to observe your technique."
Even without nopal or gher to distort his judgment, there could never be a camaraderie between Earthman and Xaxan, thought Burke. At their best they showed no more warmth or sympathy than a lizard. Without comment he took up the pillow of nopal-stuff and in quick succession crushed the three nopal, matting the fragments over the crested skulls. Then without warning he did the same for Margaret. She gasped, collapsed into her chair.
Apiptix paid her no heed. "These men are now insulated from further nuisance?"
"So far as I know. Neither nopal nor the gher seem able to penetrate the mat."
Pttdu Apiptix stood silent, evidently peering into the para-cosmos. After a moment his chest plates gave a rattle of annoyance. "The gher does not appear clearly to my visual organ. And you see it well?"
"Yes," said Burke. "When I concentrate on seeing it."
"And you can define its direction."
Burke pointed, up and off at a slant. Pttdu Apiptix turned to Tarbert. "You are agreed as to this?"
Tarbert nodded. "That's where I see it, too."
The horny chest-plates gave another rattle of annoyance. "Your visual system differs from mine. To me it appears"— the voice-box chattered as it came upon an untranslatable idea—"in all directions." He stood silently a moment, then said, "The gher has caused my people great hardship."
Something of an understatement, thought Burke. He went to the window. The eastern sky was dim with approaching dawn.
Apiptix turned to Tarbert. "You made remarks about the gher, which I failed to comprehend. Will you repeat them?"
"With pleasure," said Tarbert politely, and Burke grinned to himself. "The para-cosmos apparently is subsidiary to the normal universe. The gher would therefore seem to be the analogue of a material creature. The same of course applies to the nopal."
Apiptix stood quiet, as he digested the implications of the statement. His voice-box spoke. "I see the truth of all this. It is a great truth. We must seek out this beast and destroy it. Then we must do the same for the nopal. We will find their home environment and destroy it, and in this manner destroy the nopal."
Burke turned away from the window. "I'm not sure that this is an unalloyed blessing. It might do the Earth people great harm."
"In what way?"
"Consider the consequences if everyone on Earth suddenly becomes clairvoyant and telepathic?"
"Chaos," muttered Tarbert. "Divorces by the hundreds."
"No matter," said Apiptix. "This must not be considered. Come."
" 'Come'?" asked Burke in surprise. "Where?"
"To our space-ship." He made a motion. "Hurry. Daylight is almost here."
"We don't want to go aboard your space-ship," argued Tarbert in the voice of one reasoning with a petulant child. "Why should we?"
"Because your brains see into the over-world. You will lead us to the gher."
Burke protested; Tarbert argued; Margaret sat in apathy. Apiptix made a peremptory gesture. "Be quick. Or you will be killed."
The flat intonations gave the threat a dire and immediate significance. Burke, Tarbert and Margaret hastily walked from the building.

XII
the xaxan space-ship was a long flattened cylinder, with a row of turrets along the top surface. The interior was harsh and comfortless and smelled of Xaxan materials and of the acrid leathery odor of the Xaxans themselves. Above, cat-walks communicated with the turrets. Forward, were controls, dials, gauges, instruments; to the stern, were engines hooded under pods of pinkish metal. The three Earth-people were assigned no specific quarters and none seemed available for any members of the crew. When not occupied with one duty or another, the Xaxans sat stolidly on benches, occasionally exchanging a rattle of conversation.
Apiptix spoke only once to the Earth-people: "In which direction lies the gher?"
Tarbert, Burke and Margaret concurred that the gher was to be found in that direction marked by the constellation Perseus.
"How far, or is this revealed to you?"
None of the three could hazard so much as a guess.
"In this case we will proceed until there is a sensible change in its direction." The Xaxan marched away.
Tarbert sighed ruefully. "Will we ever see Earth again?"
"I wish I knew," said Burke.
Margaret said, "Not even a toothbrush. Not even a change of underclothes."
"You might borrow something of the sort from one of the Xaxans," Burke suggested. "Apiptix is lending Tarbert his electric razor."
Margaret gave him a sour smile. "Your humor is just a trifle misplaced."
"I'd like to know how all of this works," said Tarbert, looking up and down the compartment. "The propulsion system is like nothing I've ever heard of." He signaled Apiptix, who after an impersonal and incurious stare, approached. "Perhaps you'll explain the working of the engines to us," Tarbert suggested.
"I know nothing of this matter," stated the voice-box. "The ship is very old; it was built before the great wars."
"We'd like to learn how the engines operate," said Burke. "As you know, we don't even recognize velocities higher than light-speed."
"You may look as you like," said Apiptix, "because there is nothing to see. As to sharing our technology with you, I think it unlikely. You are a volatile and tendentious race; it is not to our interest that you over-run the galaxy." He stalked away.
"A graceless set of barbarians," growled Tarbert.
"They don't display much charm, for a fact," said Burke. "On the other hand they don't seem afflicted with any of the human vices."
"A noble race," said Tarbert. "Would you want your sister to marry one?"
Conversation lapsed. Burke tried to look into the para-cosmos. He realized a dim image of the ship, which might have been a function of the image-forming faculty of his mind rather than "clairvoyance," but no more. Beyond was darkness.
From sheer fatigue the three slept. When they awoke, they were fed, but otherwise ignored. They wandered the ship without hindrance, and found mechanisms of incomprehensible purpose, fabricated by methods and procedures which seemed quaint and strange.

The voyage continued, and only the motion of hour—and minute—hands gave a measure of time. Twice the Xaxans performed some operation which allowed the ship to coast in normal interstellar space, in order that the Earth-people could indicate the direction of the gher, after which the course was adjusted and the ship urged once again into motion. During these halts it seemed as if the gher had relaxed from its previous baleful concentration. The yellow orb floated at the top, like an egg yolk in a cup of ink. As to its distance, this was yet indefinite; in the para-cosmos "distance" had no precise measurement, and Burke and Tarbert uneasily contemplated the possibility that the gher might inhabit a remote galaxy. But on the third half, the gher no longer hung before them, but to the stern, in the precise direction of a dim red star. The gher now was enormous and brooding, and even as they gazed at the black hulk the yellow orb came tumbling around to occupy the frontal surface. It was difficult to evade a sensation that this was an organ of perception.
The Xaxans turned the ship, proceeded back along the way they had come. When they next brought it out of quasi-space, the red star hung below, attended by a single cool planet. Focusing his perceptions, Burke saw the loom of the gher superimposed upon the disk of the planet.
Here was the home of the gher. The landscape of the planet dominated the background: a dark strange land of faintly iridescent swamps and regions of what seemed cracked and caked mud. The gher occupied the center of the landscape, its filaments spreading in all directions, the orb rolling and pulsing.
The ship went into orbit around the planet. The surface, by telescopic magnification, appeared flat, almost featureless, marked by an occasional oily swamp. The atmosphere was rare, cold and mephitic. At the poles were tumbles of a black crusty substance, like charred paper. There was nothing to indicate the presence of life, neither artifacts, ruins, or illumination; and indeed the single noteworthy feature of the planet was a great chasm in the high latitudes, a crevasse like a split in an old croquet ball.
Burke, Tarbert, Pttdu Apiptix and three other Xaxans arrayed themselves in air-suits, entered the tender. It detached itself from the ship and drifted down toward the surface. Burke and Tarbert, examining the flat panorama, finally agreed on the location of the gher: a small lake or pond at the center of a wide basin, into which the sunlight struck at a long slant.
The tender keened through the upper atmosphere, settled upon a low knoll a half-mile from the pond.
The group alighted into the wan red sunlight, to stand upon a surface of shale and gravel. A few yards distant was a black knee-high growth of what seemed lichen: a crumbling efflorescence, like carbonized cabbage leaves. The sky was purple above, shading to a sulphurous brown at the horizons; the basin was a dismal expanse tinted maroon by the sunlight. At the center, the ground became moist and black, altered first to a glistening slime, then finally to liquid. Humping from the surface was a leathery black sac.
Tarbert pointed. "There is the gher."
"Insignificant, isn't it," said Burke, "compared to its analogue."
Apiptix blinked and stared into the para-cosmos. "It knows we are here."
"Yes," said Burke. "It definitely does. It's quite agitated."
Apiptix brought forth his weapon, strode off down the slope. Burke and Tarbert followed, then halted in wonder. In the para-cosmos the gher heaved and convulsed, then began to exude a vapor, which ordered itself into a tall shadow: a semi-human shadow towering—how far? A mile? A million miles? The gher seemed to loosen, to relax while the shadow condensed, absorbing substance from the gher. It became hard and dense. Burke and Tarbert called out in trepidation. Apiptix swung around. "What is the matter?"
Burke pointed into the sky. "The gher is building something. A weapon."
"In the para-cosmos? How can it hurt us?"
"I don't know. If it concentrates enough weak energy— billions of ergs—"
"That's what it's doing!" cried Tarbert. "There it is!"
A hundred feet ahead appeared a dense black bipedal body, something like a headless gorilla, eight or ten feet tall. It had long arms ending in pincers; the feet were equipped with talons. It hopped forward with sinister intent.
Apiptix and the Xaxans aimed their weapons. A purple blaze struck at the gher-creature, which gave no sign of hurt. Giving a great bound it leapt at the foremost Xaxan. Whether through discipline, fanatic courage or hysteria the Xaxan met its charge, grappled it hand to hand. The fight was short and horrid; the Xaxan was torn apart and his viscera scattered across the caked gray mud. His weapon fell at Tarbert's feet. Tarbert seized it and yelled in Burke's ear: "The gher!" and set off at a shambling run toward the pond. Burke's knees were like jelly. With great effort he forced himself to follow.
The monster stood rocking on its black legs, torso glowing in the blaze of the Xaxan weapons. Then it turned and lumbered after Tarbert and Burke, who ran across the oozing surface in an episode as terrifying and unreal as the most fearful of nightmares.
Smoking and torn, the creature caught up with Burke, struck him a blow that knocked him cart-wheeling, and continued after Tarbert, who slogged with great effort across the glistening slime. Denser and heavier, the monster floundered but lurched forward. Burke picked himself up, looked wildly around. Tarbert, now in range of the gher, aimed the unfamiliar weapon. The black creature stalked forward; Tarbert turned a fearful glance over his shoulder, and still fumbling with the weapon tried to dodge aside. His feet slid in the muck; he fell. The monster leapt forward, tramped upon Tarbert, then reached down with its pincers. Burke, staggering forward, grappled the creature from the rear. It felt as hard as stone, and as heavy, but Burke was able to thrust it off-balance, and it too toppled into the slime. Burke groped for the weapon, found it, frantically tried to find the trigger. The monster pulled itself erect and plunged at Burke, pincers wide. Close past Burke's ear spit a stream of magenta fire. It struck the gher, which exploded. The headless black creature seemed to go porous, then fell apart into shreds and wisps. The para-cosmos fractured in a great gush of soundless energy, green and blue and white. When Burke once more regained his extra-world vision the gher was gone.
He went to Tarbert, helped him to his feet; all limped back to solid footing. The pond behind them lay flat and featureless.
"A most peculiar creature," said Tarbert, in a voice still strained and choked. "Not at all nice."
They stood looking at the pond. A breath of the cold air pushed sluggish ripples over the surface. The pool seemed barren and empty, devoid of the meaning which the presence of the gher had given it.
"It must have been a million years old," said Burke.
"A million? Maybe much older." And both Burke and Tarbert looked up at the dim red sun, appraising its past and wondering about the history of the planet. The Xaxans stood in a group not far distant, looking over the pond of the gher.
Burke spoke again. "I'd guess that when it couldn't derive sustenance from the physical world it turned to the para-cosmos and became a parasite."
"It's a strange kind of evolution," said Tarbert. "The nopal must have evolved along similar lines, probably, under similar physical conditions."

"The nopal . . . they seem such trivial creatures." And Burke turned his gaze into the para-cosmos, wondering if nopal were evident. He saw, as before, the ranked landscapes, the intricate foliations, the mapped connections, the pulsing lights. Certain far nopal—riding Xaxans? or Earth-folk? he couldn't be sure—surveyed him with malevolent distrust. Elsewhere were others, with bulging eyes and vibrating plumes. These, so it seemed, were small and undeveloped, and seemed to flow in a stately parade from somewhere near at hand. This judgment might well be faulty, so deceptive were all appraisals of distance. As he studied the nopal, wondering as to their nature and where they derived he heard Tarbert's voice. "Do you get the impression of a grotto?"
Burke peered into the para-cosmos. "I see cliffs—irregular walls. A crevasse? Would it be the same one we saw coming down?"
Apiptix called to them. "Come. We return to the ship."
His mood seemed morose. "The gher has been destroyed. There are no more Tauptu. Only Chitumih. The Chitumih have won. We will alter this."
Burke spoke hurriedly to Tarbert. "It's now or never. We've got to make a move."
"How do you mean?"
Burke nodded toward the Xaxans. "They're ready to wipe out the nopal. We've got to hold them off."
Tarbert hesitated. "Do we have any option?"
"Certainly. The Xaxans couldn't find the gher without our help. They won't be able to find the nopal. It's up to us."
"If we can get away with it. ... There's a possibility that with the gher gone they might relax, see reason."
"We can try. If reason doesn't work, we've got to use something else."
"Such as what?"
"I wish I knew."
They followed the Xaxans up the slope toward the tender. Burke stopped short. "I've had a thought." He explained his idea to Tarbert.
Tarbert was dubious. "What if the stage effects don't come off?"
"They've got to come off. I'll do the reasoning; you take Care of the persuasion."
Tarbert gave a mournful laugh. "I don't know if I can persuade that hard."
Pttu Apiptix, standing beside the tender, motioned to them brusquely. "Come. There is still our final great task: we must destroy the nopal."
"It isn't quite that simple," said Burke cautiously.
The Xaxan held his gray arms wide, fists clenched, each knuckle a knob of white bone: a gesture of exultation or triumph. The voice from the box was nevertheless flat and unaccented. "Like the gher, they must have their kernels in the base universe. You located the gher without difficulty, you shall do the same for the nopal."
Burke shook his head. "Nothing good would come of it. We've got to think of something else."
Apiptix abruptly dropped his arms, peered at Burke with topaz eyes. "I fail to understand. We must win our war."
"Two worlds are involved. We must consider the best interests of both. For Earth any sudden destruction of the nopal would mean disaster. Our society is based upon individuality, privacy of thought and intent. If everyone suddenly achieved a psionic capacity, our civilization would become chaos. Naturally we do not care to inflict this disaster upon our planet."
"Your wishes are immaterial! We are the ones who have suffered and you must follow our instructions."
"Not when they're irrational and irresponsible."
The Xaxan considered him a moment. "You are bold. You must know that I can force you to obey me."
Burke shrugged. "Conceivably."
"You would tolerate these parasites?"
"Not permanently. In the course of years we shall either destroy them or make them socially useful. Before this happens we'll have had time to adjust ourselves to psionic realities. And another consideration: we have our own war on Earth—the 'cold war,' against a particularly odious kind of enslavement. With psionic capabilities, we can easily win this war, with a minimum of bloodshed, to the ultimate benefit of everyone. For us, we gain nothing and lose everything by destroying the nopal—at this moment."
The flat tones of the Xaxan's voice-box were almost sardonic. "As you remarked, the interests of two worlds are involved."
"Precisely. To destroy the nopal would injure your world as much as ours."
Apiptix jerked back his head in surprise. "Absurd! After a hundred and twenty years you expect us to stop short of our goal?"
"You are obsessed with the nopal," said Burke. "You forget the gher, which forced the war upon you."
Apiptix looked off toward the sullen pond. "The gher is dead. The nopal remain."
"Which is fortunate, since they may be crushed and used as protection—against themselves and all the other parasites of the para-cosmos."
"The gher is dead. We shall destroy the nopal. Then we will need no more protection."
Burke gave a short laugh. "Now who's absurd?" He pointed to the sky. "There are millions of worlds like this one. Do you think the gher and the nopal are unique, the only creatures who inhabit the para-cosmos?"
Apiptix drew back his head like a startled turtle. "There are others?"
"Look for yourself."
Apiptix stood rigid, straining to perceive the para-cosmos. "I see shapes I cannot understand. One in particular—an evil creature . . ." He looked at Tarbert who stood staring fixedly into the sky, then returned to Burke. "Do you see this creature?"
Burke looked into the sky. "I see something almost like the gher. ... It has a bulging body, two large eyes, a beaked nose, long tentacles. . . ."
"Yes. This is what I see." Apiptix stood silently. "You are right. We need the nopal for protection. Temporarily at least. Come; we will return."
He marched away up the slope. Burke and Tarbert came behind. "You project a vivid octopus," said Burke. "It even gave me a twinge."
"I almost tried a Chinese dragon," said Tarbert. "The octopus was probably more legitimate."
Burke halted, searched the para-cosmos. "We really weren't conning him. Not altogether. There must be other things like nopal and gher. I seem to see something far far away— like a tangle of angle-worms. . . ."
"Sufficient into the day the evil thereof," said Tarbert in sudden exhilaration. "Let's go home and scare hell out of the commies."
"A noble thought," said Burke. "We've also got a hundred kilograms of gold in the back of my car."
"Who needs gold? All we need is clairvoyance and the black-jack tables at Las Vegas. It's a system nobody can beat."
The tender swung up from the ancient planet, slanting across the great crevasse which split the surface to an unknown depth. Looking down Burke saw puffs and plumed shapes drifting up, moving across space to a place in the para-cosmos where a distorted but familiar globe shone a lambent greenish-yellow.
"Dear old Nopalgarth," said Burke. "Here we come."