Garry looked about the crowded room. Thirty-two men, some tensed nervously standing against the wall, some uneasily relaxed, some sitting, most perforce standing, as intimate as sardines. Thirty-two, plus the five engaged in sewing up wounded dogs, made thirty-seven, the total personnel.

Garry started speaking. "All right, I guess we're here. Some of you--three or four at most--saw what happened. All of you have seen that thing on the table, and can get a general idea. Anyone hasn't, I'll lift--" His hand strayed to the tarpauling bulking over the thing on the table. There was an acrid odor of singed flesh seeping out of it. The men stirred restlessly, hasty denials.

"It looks rather as though Charnauk isn't going to lead any more teams," Garry went on. "Blair wants to get at this thing, and make some more detailed examination. We want to know what happened, and make sure right now that this is permanently, totally dead. Right?"

Connant grinned. "Anybody that doesn't agree can sit up with it tonight."

"All right then, Blair, what can you say about it? What was it?" Garry turned to the little biologist.

"I wonder if we ever saw its natural form." Blair looked at the covered mass. "It may have been imitating the beings that built that ship--but I don't think it was. I think that was its true form. Those of us who were up near the bend saw the thing in action; the thing on the table is the result. When it got loose, apparently, it started looking around. Antarctica still frozen as it was ages ago when the creature first saw it--and froze. From my observations while it was thawing out, and the bits of tissue I cut and hardened then, I think it was native to a hotter planet than Earth. It couldn't, in its natural form, stand the temperature. There is no life-form on earth that can live in Antarctica during the winter, but the best compromise is the dog. It found the dogs, and somehow got near enough to Charnauk to get him. The others smelled it--heard it--I don't know--anyway they went wild, and broke chains, and attacked it before it was finished. The thing we found was part Charnauk, queerly only half-dead, part Charnauk half-digested by the jellylike protoplasm of that creature, and part the remains of the thing we originally found, sort of melted down to the basic protoplasm.

"When the dogs attacked it, it turned into the best fighting thing it could think of. Some other-world beast apparently."

"Turned," snapped Garry. "How?"

"Ever living thing is made up of jelly--protoplasm and minute, submicroscopic things called nuclei, which control the bulk, the protoplasm. This thing was just a modification of that same worldwide plan of Nature; cells made up of protoplasm, controlled by infinitely tinier nuclei. You physicists might compare it--an individual cell of any living thing--with an atom; the bulk of the atom, the space-filling part, is made up of electron orbits, but the character of the thing is determined by the atomic nucleus.

"This isn't wildly beyond what we already know. It's just a modification we haven't seen before. It's as natural, as logical, as any other manifestation of life. It obeys exactly the same laws. The cells are made of protoplasm, their character determined by the nucleus.

"Only in this creature, the cell-nuclei can control those cells at will. It digested Charnauk, and as it digested, studied every cell of his tissue, and shaped its own cells to imitate them exactly. Parts of it--parts that had time to finish changing--are dog-cells. But they don't have dog-cell nuclei." Blair lifted a fraction of the tarpaulin. A torn dog's leg with stiff gray fur protruded. "That, for instance, isn't dog at all; it's imitation. Some parts I'm uncertain about; the nucleus was hiding itself, covering up with dog-cell imitation nucleus. In time, not even a microscope would have shown the difference."

"Suppose," asked Norris bitterly, "it had had lots of time?"

"Then it would have been a dog. The other dogs would have accepted it. We would have accepted it. I don't think anything would have distinguished it, not microscope, nor X-ray, nor any other means. This is a member or a supremely intelligent race, a race that has learned the deepest secrets of biology, and turned them to its use."

"What was it planning to do?" Barclay looked a the humped tarpaulin.

Blair grinned unpleasantly. The wavering halo of thin hair round his bald pate wavered in the stir of air. "Take over the world, I imagine."

"Take over the world! Just it, all by itself?" Connant gasped. "Set itself up as a lone dictator?"

"No," Blair shook his head. The scalpel he had been fumbling in his bony fingers dropped; he bent to pick it up, so that his face was hidden as he spoke. "It would become the population of the world."

"Become--populate the world? Does it reproduce asexually?"

Blair shook his head and gulped. "It's--it doens't have to. It weighed 85 pounds. Charnauk weighed about 90. it would have become Charnauk, and had 85 pounds left, to become--oh, Jack for instance, or Chinook. It can imitate anything--that is, become anything. If it had reached the Antarctic Sea, it would have become a seal, maybe two seals. They might have attacked a killer whale, and become either killers, or a herd of seals. Or maybe it would have caught an albatross, or a skua gull, and flown to South America."

Norris cursed softly. "And every time it digested something, and imitated it--"

"It would have had its original bulk left, to start again," Blair finished. "Nothing would kill it. It has no natural enemies, because it becomes whatever it wants to. If a killer whale attacked it, it would become a killer whale. If it was an albatross, and an eagle attacked it, it would become an eagle. Lord, it might become a female eagle. Go back--build a nest and lay eggs!"

"Are you sure that thing from hell is dead?" Dr. Copper asked softly.

"Yes, thank Heaven," the little biologist gasped. After they drove the dogs off, I stood there poking Bar's electrocution thing into it for five minutes. It's dead and--cooked."

"Then we can only give thanks that this is Antarctic, where there is not one, single, solitary, living thing for it to imitate, except these animals in camp."

"Us," Blair giggled. "It can imitate us. Dogs can't make four hundred miles to the sea; there's no food. There aren't any skua gulls to imitate at this season. There aren't any penguins this far inland. There's nothing that can reach the sea from this point--except us. We've got brains. We can do it Don't you see--it's got to imitate us--it's got to be one of us--that's the only way it can fly an airplane--fly a plane for two hours, and rule--be--all Earth's inhabitants. A world for the taking-- if it imitates us!

"It didn't know yet. It hadn't had a chance to learn. It was rushed--hurried--took the thing nearest its own size. Look--I'm Pandora! I opened the box! And the only hope that can come out is--that nothing can come out. You didn't see me. I did it. I fixed it. I smashed every magneto. Not a plane can fly. Nothing can fly." Blair giggled and lay down on the floor crying.

Chief Pilot Van Wall made a dive for the door. His feet were fading echoes in the corridors as Dr. Copper bent unhurriedly over the little man on the floor. From his office at the end of the room he brought something, and injected a solution into Blair's arm. "He might come out of it when he wakes up," he sighed, rising. McReady helped him lift the biologist onto a nearby bunk. "It all depends on whether we can convince him that thing is dead."

Van Wall ducked into the shack brushing his heavy blond beard absently. "I didn't think a biologist would do a thing like that up thoroughly. He missed the spares in the second cache. It's all right. I smashed them."

Commander Garry nodded. "I was wondering about the radio."

Dr. Copper snorted. "You don't think it can leak out on a radio wave, do you? You'd have five rescue attempts in the next three months if you stop the broadcasts. The thing to do is talk loud and not make a sound. Now I wonder--"

McReady looked speculatively at the doctor. "It might be like an infectious disease. Everything that drank any of its blood--"

Copper shook his head. "Blair missed something. Imitate it may, but it has to a certain extent, its own body-chemistry, its own metabolism. If it didn't, it would become a dog--and be a dog and nothing more. It has to be an imitation dog. Tehre you can detect it by serum test. And its chemistry, since it comes from another world, must be so wholly, radically different that a few cells, such as gained by drops of blood, would be treated as diease germs by the dog, or human body."

"Blood--would one of those imitations bleed?" Norris demanded.

"Surely. Nothing mystic about blood. Muscle is about 90 percent water, blood differs only in having a couple percent more water, and less connective tissue. They'd bleed all right," Copper assured him.

Blair sat up in his bunk suddenly. "Connant--where's Connant?"

The physicist moved over toward the little biologist. "Here I am. What do you want?"

"Are you?" giggled Blair. He lapsed back into his bunk contorted with silent laughter.

Connant looked at him blankly. "Huh? Am I what?"

"Are you there?" Blair burst into gales of laughter. "Are you Connant? The beast wanted to be a man--not a dog--"

Dr. Copper rose wearily from the bunk, and washed the hypodermic carefully. The little tinkles it made seemed loud in the packed room, now that Blair's gurgling laughter had finally quieted. Copper looked toward Garry and shook his head slowly. "Hopeless, I'm afraid. I don't think we can ever convince him the thing is dead now."

Norris laughed uncertainly. "I'm not sure you can convince me. Oh, damn you, McReady."

"McReady?" Commander Garry turned to look from Norris to McReady curiously.

"The nightmares," Norris explained. "He had a theory about the nightmares we had at the Secondary Station after finding that thing."

"And that was?" Garry looked at McReady levelly.

Norris answered for him, jerkily, uneasily. "That the creature wasn't dead, had a sort of enormously slowed existence, an existence that permitted it, none the less, to be vaguely aware of the passing of time, of our coming, after endless years. I had a dream it could imitate things."

"Well," Copper grunted, "it can."

"Don't be an ass," Norris snapped. "That's not what's bothering me. In the dream it could read minds, read thoughts and ideas and mannerisms."

"What's so bad about that? It seems to be worrying you more than the thought of the joy we're going to have with a mad man in an Antarctic camp." Copper nodded toward Blair's sleeping form.

McReady shook his great head slowly. "You know that Connant is Connant, because he not merely looks like Connant--which we'ere beginning to believe that beast might be able to do--but he thinks like Connant, talks like Connant, moves himself around as Connat does. That takes more than merely a body that looks like him; that takes Connant's own mind, and thoughts and mannerisms. Therefore, though you know that the thing might make itself look like Connant, you aren't much bothered, because you know it has a mind from another world, a totally unhuman mind, that couldn't possibly react and think and talk like a man we know, and do it so well as to fool us for a moment. The idea of the creature imitating one of us is fascinating but unreal because it is too completely unhuman to deceive us. It doesn't have a human mind."

"As I said before," Norris repeated, looking steadily at McReady, "you can say the damnedest things at the damnedest times. Will you be so good as to finish that thought--one way or the other?"

Kinner, the scar-face expedition cook, had been standing near Connant. Suddenly he moved down the length of the crowded room toward his familiar galley. He shook the ashes from the galley stove noisily.

"It would it no good," said Dr. Copper, softly as though thinking out loud, "to merely look like something it was trying to imitate; it would have to understand its feelings, its reaction. It is unhuman; it has powers of imitation beyond any conception of man. A good actor, by training himself, can imitate another ma, another man's mannerisms, well enough to fool most people. Of course no actor could imitate so perfectly as to deceive men who had been living with the imitated one in the complete lack of privacy of an Antarctic camp. That would take a super-human skill."

"Oh, you've got the bug too?" Norris cursed softly.

Connant, standing alone at one end of the room, looked about him wildly, his face white. A gentle eddying of the men had crowded them slowly down toward the other end of the room, so that he stood quite alone. "My God, will you two Jeremiahs shut up?" Connant's voice shook. "What am I? Some kind of a microscopic specimen you're dissecting? Some unpleasant worm you're discussing in the third person?"

McREady looked up at him; his slowly twisting hands stopped for a moment. "Having a lovely time. Wish you were here. Signed: Everybody. "Connant, if yo think you're having a hell of a time, just move over on the other end for a while. You've got one thing we haven't; you know what the answer is. I'll tell you this, right now you're the most feared an respected man in Big Magnet."

"Lord, I wish you could see your eyes," Connant gasped "Stop staring, will you? What the hell are you going to do?"

"Have any suggestions, Dr. copper?" Commander Garry asked steadily. "The present situation is impossible."

"Oh, is it?" Connant snapped. "Come over here and look at that crowd. By Heaven, they look exactly like that gang of huskies around the corridor bend. Benning, will you stop hefting that damned ice-ax?"

The coppery blade rang on the floor as the aviation mechanic nervously dropped it. He bent over and picked it up instantly, hefting it slowly, turning it in his hands, his brown eyes moving jerkily about the room.

Copper sat down on the bunk beside Blair. The wood creaked noisily in the room. Far down a corridor, a dog yelped in pain, and the dog-drivers' tense voices floated softly back. "Microscopic examination," said the doctor thoughtfully, "would be useless, as Blair pointed out. Considerable time has passed. However, serum tests would be definitive."

"Serum tests? What do you mean exactly?" Commander Garry asked.

"If I had a rabbit that had been injected with human blood--a poison to the rabbits, of course, as is the blood of any animal save that of another rabbit--and the injections continued in increasing doses for some time, the rabbit would be human-immune. If a small quantity of its blood were drawn off, allowed to separate in a test-tube, and to the clear serum, a bit of human blood were added, there would be a visible reaction, proving the blood was human. If cow, or dog blood were added--or any protein material other than that one thing, human blood--no reaction would take place. That would prove definitely."

"Can you suggest where I might catch a rabbit for you, Doc?" Norris asked. "That is, nearer than Australia; we don't want to waste time going that far."

"I know there aren't any rabbits in Antarctica," Copper nodded, "but that is simply the usual animal. Any animal except man will do. A dog for instance. But it will take several days, and due to the greater size of the animal, considerable blood. Two of us will have to contribute."

"Would I do?" Garry asked.

"That will make two," Copper nodded. "I'll get to work on it right away."

"What about Connant in the meantime?" Kinner demanded. "I'm going out that door and head off for the Ross Sea before I cook for him."

Connant burst out in a flood of curses. "Human! May be human, you damned saw-bones! What in hell do you think I am?"

"A monster," Copper snapped sharply. "Now shut up and listen." Connant's face drained of color and he sat down heavily as the indictment was put in words. "Until we know--you know as well as we do that we have reason to question the fact, and only you know how that question is to be answered--we may reasonably be expected to lock you up. If you are--unhuman--you're a lot more dangerous than poor Blair there, and I'm going to see that he's locked up thoroughly. I expect that his next stage will be a violent desire to kill you, all the dogs, and probably all of us. When he wakes, he will be convinced we're all unhuman, and nothing on the planet will ever change his conviction. It would be kinder to let him die, but we can't do that, of course. He's going in one shack, you can stay in Cosmos House with your cosmic ray apparatus. Which is about what you'd do anyway. I've got to fix up a couple of dogs."

Connant nodded bitterly. "I'm human. Hurry that test. Your eyes--Lord, I wish you could see your eyes staring--"

Commander Garry watched anxiously as Clark, the dog-handler, held the big brow Alaskan husky, while Copper began the injection treatment. The dog was not anxious to cooperate; the needle was painful, an already he'd experienced considerable needle work that morning. Five stitches held closed a slash that ran from his shoulder across the ribs half way down his body. One long fang was broken off short; the missing part was to be found half-buried in the shoulder bone of the monstrous thing on the table in the Ad Building.

"How long will that take?" Garry asked, pressing his arm gently. It was sore from the prick of the needle Dr. Copper had used to withdraw blood.

Copper shrugged. "I don't know, to be frank. I know the general method, I've used it on rabbits. But I haven't experimented with dogs. They're big, clumsy animals to work with; naturally rabbits are preferable, and serve ordinarily. In civilized places you can buy a stock of human-immune rabbits from suppliers, and not many investigators take the trouble to prepare their own."

"What do they want them back there?" Clark asked.

"Criminology is one large filed. A says he didn't murder B, but that the blood on his shirt came from killing a chicken. That State make a test, then it's up to A to explain how it is the blood reacts on human-immune rabbits, but not on chicken-immunes."

"What are we going to do with Blair in the meantime?" Garry asked wearily. "It's all right to let him sleep where he is for a while, but when he wakes up--"

"Barclay and Benning are fitting some bolts on the door of Cosmos House," Copper replied grimly. "Connant's acting like a gentleman. I think perhaps the way the other men look at him makes him rather want privacy. Lord knows, heretofore we've all of us individually prayed for a little privacy."

Clark laughed bitterly. "Not anymore, thank you. The more the merrier."

"Blair," Copper went on, 'will also have to have privacy--and locks. He's going to have a pretty definite plan in mind when he wakes up. Ever hear the old story of how to stop hoof-and-mouth disease in cattle?

"If there isn't any hoof-and-mouth disease, there won't be any hoof-and-mouth disease," Copper explained. "You get rid of it by killing every animal that exhibits it, and every animal that's been near the diseased animal. Blair's a biologist, and knows that story. He's afraid of this thing we loosed. The answer is probably pretty clear in his mind now. Kill everybody and everything in this camp before a skua gull or a wandering albatross coming in with the spring chances out this way and--catches the disease."

Clark's lips curled in a twisted grin. "Sounds logical to me. If things get too bad--maybe we'd better let Blair get loose. It would save us committing suicide. We might also make something of a vow that if things get bad, we see that that does happen."

Copper laughed softly. "The last man alive in Big Magnet--wouldn't be a man," he pointed out. "Somebody's got to kill those--creatures that don't desire to kill themselves, you know. We don't have enough thermite to do it all at once, and the decanite explosive wouldn't help much. I have an idea that even small pieces of one of those beings would be self-sufficient."

"If," said Garry thoughtfully, "they can modify their protoplasm at will, won't they simply modify themselves to birds and fly away? They can read all about birds, and imitate their structure without even meeting them. Or imitate, perhaps, birds of their home planet."

Copper shook his head, and helped Clark to free the dog. "Man studied birds for centuries, trying to learn how to make a machine to fly like them. He never did do the trick; his final success came when he broke away entirely and tried new methods. Knowing the general idea, and knowing the detailed structure of wing and bone and nerve-tissue is something far, far different. And as for other-world birds, perhpas, in fact very probably, the atmospheric conditions here are so vastly different that their birds couldn't fly. Perhaps, even, the being came from a planet like Mars with such a thin atmosphere that there were no birds."

Barclay came into the building, trailing a length of airplane control cable. "It's finished, Doc. Cosmos HOuse can't be opened from the inside. Now where do we put Blair?"

Copper looke toward Garry. "There wasn't any biology building. I don't know where we can isolate him."

"How about East Cache?" Garry said after a moment's thought. "Will Blair be able to look after himself--or need attention?"

"He'll be capable enough. We'll be the ones to watch out," Copper assured him grimly. "Take a stove, a couple bags of coal, necessary supplied and a few tools to fix it up. Nobody's been there since last fall, have they?"

Garry shook his head. "If he gets noisy--I thought that might be a good idea."

Barclay hefted the tools he was carrying and looked up at Garry. "If the muttering he's doing now is any sign, he's going to sing away the night hours. And he won't like his song."

"What's he saying?" Copper asked.

Barclay shook his head. "I didn't care to listen much. You can if you want to. But I gathered that the blasted idiot had all the dreams. McReady had, and a few more. He slept beside the thing when we stopped on the trail coming in from Secondary Magnetic, remember. He dreamt the thing was alive, and dreamt more details. And--damn his soul--knew it wasn't all dream, or had reason to. HE knew it had telepathic powers that were stirring vaguely, and that it could not only read minds, but project thoughts. They weren't dreams, you see. They were stray thoughts that thing was broadcasting, the way Blair's broadcasting his thoguhts now--a sort of telepathic muttering in its sleep. That's why he knew so much about its powers. I guess you and I, Doc, weren't so sensitive--if you want to believe in telepathy."

"I have to," Copper sighted. "Dr. Rhine of Duke University has shown that it exist, shown that some are much more sensitive than others."

"Well, if you want to learn a lot of details, go listen in on Blair's broadcast. He's drive most of the boys out of the Ad Building; Kinner's rattling pans like coal going down a chute. When he can't rattle a pan, he shakes ashes.

"By the way, Commander, what are we going to do this spring, now the planes are out of it?"

Garry sighted. "I'm afraid out expedition is going to be a loss. We cannot divide our strength now."

"It won't be a loss--if we continue to live, and come out of this," Copper promised him. "The find we've made, if we can get it under control, is important enough. The cosmic ray data, magnetic work, and atmospheric work won't be greatly hindered."

Garry laughed mirthlessly. "I was just thinking of the radio broadcasts. Telling half the world about the wonderful results of our exploration flights, trying to fool men like Byrd and Ellsworth back home there that we're doing something."

Copper nodded gravely. "They'll know something's wrong. But men like that have judgment enough to know we wouldn't do tricks without some sort of reason, and will wait for our return to judge us. I think it comes to this: men who know enough to recognize our deception will wait for our return. Men who haven't discretion and faith enough to wait will not have the experience to detect any fraud. WE know enough of the conditions here to put through a good bluff."

"Just so they don't send 'rescue' expeditions," Garry prayed. "When--if--we're ever ready to come out, we'll have to send word to Captain Forsythe to bring a stock of magnetos with him when he comes down. But--never mind that."

"You mean if we don't come out?" asked Barclay. "I was wondering if a nice running account of an eruption or an earthquake via radio--with a sell windup by using a stick of decanite under the microphone--would help. Nothing, of course, will entirely keep people out. One of those swell, melodramatic 'last-man-alive-scenes' might make 'em go easy though."

Garry smiled with genuine humor. "Is everybody in camp trying to figure that out too?"

Copper laughed. "What do you think, Garry? We're confident we can win out. But not too easy about it, I guess."

Clark grinned up from the dog he was petting into calmness. "Confident did you say, Doc?"

Blair moved restlessly around the small shack. His eyes jerked and quivered in vague, fleeting glances at the four men with him; Barclay, six feet tall and weighing over 190 pounds; McReady, a bronze giant of a man; Dr. Copper, short, squatly powerful; and Benning, five-feet-ten of wiry strength.

Blair was huddled up against the far wall of the East Cache cabin, his gear piled in the middle of the floor beside the heating stove, forming an island between him and the four men. His bony hands clenched and fluttered, terrified. His pale eyes wavered uneasily as his bald, freckled head darted about in birdlike motion.

"I don't want anybody coming here. I'll cook my own food," he snapped nervously. "Kinner may be human now, but I don't believe it. I'm going to get out of here, but I'm not going to eat any food you send me. I want cans. Sealed cans."

"O.K., Blair, we'll bring 'em tonight," Barclay promised. "You've got coal, and the fire's started. I'll make a last--" Barclay started forward.

Blair instantly scurried to the farthest corner. "Get out! Keep away from me, you monster!" the little biologist shrieked, and tried to claw his way through the wall of the shack. "Keep away from me--keep away--I won't be absorbed--I won't be--"

Barclay relaxed and moved back. Dr. Copper shook his head. "Leave him alone, Bar. It's easier for him to fix the thing himself. We'll have to fix the door, I think--"

The four men let themselves out. Efficiently, Benning and Barclay fell to work. There were no locks in Antarctica; there wasn't enough privacy to make them needed. But powerful screws had been driven in each side of the doorframe, and the spare aviation control cable, immensely strong, woven steel wire, was rapidly caught between them and drawn taut. Barclay went to work with a drill and a keyhole saw. Presently he had a trap cut in the door through which goods could be passed without unlashing the entrance. Three powerful hinges from a stock-crate, two hasps and a pair of three-inch cotter-pins made it proof against opening from the other side.

Blair moved about restlessly inside. He was dragging something over to the door with panting gasps and muttering, frantic curses. Barclay opened the hatch and glanced in, Dr. Copper peering over his shoulder. Blair had moved the heavy bunk against the door. It could not be opened without his cooperation now.

"Don't know but what the poor man's right at that," McReady sighed. "If he gets loose, it is his avowed intention to kill each and all of us as quickly as possible, which is something we don't agree with. But we've something on our side of that door that is worse than a homicidal maniac. If one or the other has to get loose, I think I'll come up and undo those lashings here."

Barclay grinned. "You let me know, and I'll show you how to get these off fast. Let's go back."

The sun was painting the northern horizon in multi-colored rainbows still, though it was two hours below the horizon. The field of drift swept off to the north, sparkling under its flaming colors in a million reflected glories. Low mounds of rounded white on the northern horizon showed the Magnet Range was barely awash above the sweeping drift. Little eddies of wind-lifted snow swirled away from their skis as they set out toward the main encampment tow miles away. The spidery finger of the broadcast radiator lifted a gaunt black needle against the white of the Antarctic continent. The snow under their skis was like fine sand, hard and gritty.

"Spring," said Benning bitterly, "is come. Ain't we got fun! I've been looking forward to getting away from this blasted hole in the ice."

"I wouldn't try it now, if I were you." Barclay grunted. "Guys that set out from here in the next few days are going to be marvelously unpopular."

"How is your dog getting along, Dr. Copper?" McReady asked. "Any results yet?"

"In thirty hours? I wish there were. I gave him an injection of my blood today. But I imagine another five days will be needed. I don't know certainly enough to stop sooner."

"I've been wondering--if Connant were--changed, would he have warned us so soon after the animal escaped? Wouldn't he have waited long enough for it to have a real chance to fix itself? Until we woke up naturally?" McReady asked slowly.

"The thing is selfish. You didn't think it looked as though it were possessed of a store of the higher justices, did you?" Dr. Copper pointed out. "Every part of it is all of it, every part of it is all for itself, I imagine. If Connant were changed, to save his skin, he'd have to--but Connant's feelings aren't changed; they're imitated perfectly, or they're his own. Naturally, the imitation, imitating perfectly Connant's feelings, would do exactly what Connant would do."

"Say, couldn't Norris or Van give Connant some kind of a test? If the thing is brighter than men, it might know more physics than Connant should, and they'd catch it out," Barclay suggested.

Copper shook his head wearily. "Not if it reads minds. You can't plan a trap for it. Van suggested that last night. He hoped it would answer some of the questions of physics he'd like to know answers to."

"This expedition-of-four idea is going to make life happy." Benning looked at his companions. "Each of us with an eye on the others to make sure he doesn't do something--peculiar. Man, aren't we going to be a trusting bunch! Each man eyeing his neighbors with the gradest exhibition of faith and trust--I'm beginning to know what Connant meant by 'I wish you could see your eyes.' Every now and then we all have it, I guess. One of you looks around with a sort of 'I-wonder-if-the-other-three-are look.' Incidentally, I'm not excepting myself."

"So far as we know, the animal is dead, with a slight question as to Connant. No other is suspected," McReady stated slowly. "The 'always-four' order is merely a precautionary measure."

"I'm waiting for Garry to make it four-in-a-bunk," Barclay sighed. "I thought I didn't have any privacy before, but since that order--"

None watched more tensely than Connant. A little sterile glass test-tube, half-filled with straw -colored fluid. One-two-three-four-five drops off the clear solution Dr. Copper had prepared from the drops of blood from Connant's arm. The tube was shaken carefully, then set in a beaker of clear, warm water. The thermometer read blood heat, a little thermostat clicked noisily, and the electric hotplate began to glow as the lights flickered slightly.

Then--little white flecks of precipitation were forming, snowing down the clear straw-colored fluid. "Lord," said Connant. He dropped heavily into a bunk, crying like a baby. "Six days--" Connant sobbed, "six days in there-- wondering if that damned test would lie--"

Garry moved over silently, and slipped his arms across the physicist's back.

"It couldn't lie," Dr. Copper said. "The dog was human-immuned--and the serum reacted."

"He's--all right?" Norris gasped. "Then--the animal is dead--dead forever?"

"He is human," Copper spoke deinitely, "and the animal is dead."

Kinner burst out laughing, laughing hysterically. McReady turned toward him and slapped his face with a methodical one-two, one-two action. The cook laughed, gulped, cried a moment and sat up rubbing his cheeks, mumbling his thanks vaguely. "I was scared. Lord, I was scared--"

Norris laughed bitterly. "You think we weren't, you ape? You think maybe Connant wasn't?"

The Ad Building stirred with a sudden rejuvenation. Voices laughed, the men clustering around Connant spoke with unnecessarily loud voices, jittery, nervous voices relievedly friendly again. Somebody called out a suggestion, and a dozen started for their skis. Blair. Blair might recover------Dr. Copper fussed with his test-tubes in nervous relief, trying solutions. The party of relief for Blair's shack started out the door, skis clapping noisily. Down the corridor, the dogs set up a quick yelping howl as the air of excited relief reached them.

Dr. Copper fussed with his tubes. McReady noticed him first, sitting on the edge of the bunk, with two precipitin-whitened test-tubes of straw-colored fluid, his face whiter than the stuff in the tubes, silent tears slipping down from horr-widen eyes.

McReady felt a cold knife of fear pierce through his heart and freeze in his breast. Dr. Copper looked up.

"Garry," he called hoarsely. "Garry, for God's sake, come here."

Commander Garry walked toward him sharply. Silence clapped down on the Ad Building. Connat looked up, rose stiffly from his seat.

"Garry--tissue from the monster--precipitates too. It proves nothing. Nothing but--but the dog was monster-immune too. That one of the two contributing blood--one of us two, you and I, Garry--one of us is a monster."

"Bar, call back those men before they tell Blair," McReady said quietly. Barclay went to the door; faintly his shouts came back tot he tensely silent men in the room. Then he was back.

"They're coming," he said. "I didn't tell them why. Just that Dr. Copper said not to go."

"McReady," Garry sighed, "you're in command now. May God help you. I cannot."

The bronzed giant nodded slowly, his deep eyes on Commander Garry.

"I may be the one," Garry added. "I know I'm not, but I cannot prove it to you in any way. Dr. Copper's test has broken down. The fact that he showed it was useless, when it was to the advantage of the monster to have that uselessness not known, would seem to prove he was human."

Copper rocked back and forth slowly on the bunk. "I know I'm human. I can't prove it either. One of us two is a liar, for that test cannot lie, and it says one of us is. I gave proof that the test was wrong, which seems to prove I'm human, and now Garry has given that argument which proves me human--which he, as the monster, should not do. Round and round and round and round and--"

Dr. Copper's head, then his neck and shoulders began circling slowly in time to the words. Suddenly he was lying back on the bunk, roaring with laughter. "It doesn't have to prove one of us is a monster! It doesn't have to prove that at all! Ho-ho. If we're all monsters it works the same! We're all monsters--all of us--Connant and Garry and I--and all of you."

"McReady," Van Wall, the blond-bearded Chief Pilot, called softly, "you were on the way to an M.D. when you took up meteorology, weren't you? Can you make some kind of test?"

McReady went over to Copper slowly, took the hypodermic from his hand, and washed it carefully in 95 per cent alcohol. Garry sat on the bunk-edge with wooden face, watching Copper and McReady expressionlessly. "What Copper said is possible," McReady sighted. "Van, will you help here? Thanks." The filled needle jabbed into Copper's thigh. The man's laughter did not stop, but slowly faded into sobs, then sound sleep as the morphia took hold.

McReady turned again. The men who had started for Blair stood at the far end of the room, skis dripping snow, their faces as white as their skis. Connant had a lighted cigarette in each hand; one he was puffing absently, and staring at the floor. The heat of the one in his left hand attracted him and he stared at it, and the one in the other hand, stupidly for a moment. He dropped one and crushed it under his heel slowly.

"Dr. Copper," McReady repeated, "could be right. I know I'm human--but of course can't prove it. I'll repeat the test for my own information. Any of you other who wish to may do the same."

Two minutes later, McReady held a test-tube with white precipitin settling slowly from the straw-colored serum. "It reacts to human blood too, so they aren't both monsters."

"I didn't think they were," Van Wall sighed. "That wouldn't suit the monster either; we could have destroyed them if we knew. Why hasn't the monster destroyed us, do you suppose? It seems to be loose."

McReady snorted. Then laughed softly. "Elementary, my dear Watson. The monster wants to have life-forms available. It cannot animate a dead body, apparently. It is just waiting--waiting until the best opportunities come. We who remain human, it is holding in reserve."

Kinner shuddered violently. "Hey. Hey, Mac, would I know if I was a monster? Would I know if the monster had already got me? Oh Lord, I may be a monster already."

"You'd know," McReady answered.

"But we wouldn't," Norris laughed shortly, half-hysterically.

McReady looked at the vial of serum remaining. "There's one thing this damned stuff is good for, at that," he said thoughtfully. "Clark, will you and Van help me? The rest of the gang better stick together here. Keep an eye on each other," he said bitterly. "See that you don't get into mischief, shall we say?"

McReady started down the tunnel toward Dogtown, with Clark and Van Wall behind him. "you need more serum?" Clark asked.

McReady shook his head. "Tests. There's four cows and a bull, and nearly seventy dogs down there. This stuff reacts only to human blood and--monsters."

McReady came back to the Ad Building and went silently to the wash stand. Clark and Van Wall joined him a moment later. Clark's lips had developed a tic, jerking into sudden, unexpected sneers.

"What did you do?" Connant exploded suddenly. "More immunizing?"

Clark snickered, and stopped with a hiccough. "Immunizing. Haw! Immune all right."

"That monster," said Van Wall steadily, "is quite logical. Our immune dog was quite all right, and we drew a little more serum for the tests. But we won't make any more."

"Can't--can't you use one man's blood on another dog--" Norris began.

"There aren't," said McReady softly, "any more dogs. Nor cattle, I might add."

"No more dogs?" Benning sat down slowly.

"They're very nasty when they start changing," Van Wall said precisely, "but slow. That electrocution iron you made up, Barclay, is very fast There is only one dog left--our immune. The monster left that for us, so we could play with our little test. The rest--" He shrugged and dried his hands.

"The cattle--" gulped Kinner.

"Also. Reacted very nicely. They look funny as hell when they start melting. The beast hasn't any quick escape, when it's tie in dog chains, or halters, and it had to be to imitate."

Kinner stood up slowly. His eyes darted around the room, and came to rest horribly quivering on a tin bucket in the galley. Slowly, step by step, he retreated toward the door, his mouth opening and closing silently, like a fish out of water.

"The milk--" he gasped. "I milked 'em an hour ago--" His voice broke into a scream as he dived through the door. He was out on the ice cap without windproof or heavy clothing.

Van Wall looked after him for a moment thoughtfully. "He's probably hopelessly mad," he said at length, "but he might be a monster escaping. He hasn't skis. Take a blow-torch in case."

The physical motion of the chase helped them; something that needed doing. Three of the other men were quietly being sick. Norris was lying flat on his back, his face greenish, looking steadily at the bottom of the bunk above him.

"Mac, how long have the--cows been not--cows--"

McReady shrugged his shoulders hopelessly. He went over to the milk bucket, and with his little tube of serum went to work on it. The milk clouded it, making certainty difficult. Finally he dropped the test-tube in the stand and shook his head. "It tests negatively. Which means either they were cows then, or that, being perfect imitations, they gave perfectly good milk."

Copper stirred restlessly in his sleep and gave a gurgling cross between a snore and laugh. Silent eyes fastened on him. "Would morphia--a monster--" somebody started to ask.

"Lord knows," McReady shrugged. "It affects every Earthly animal I know of."

Connant suddenly raised his head. "Mac! The dogs must have swallowed pieces of the monster, and the pieces destroyed them! The dogs were where the monster resided. I was locked up. Doesn't that prove--"

Van Wall shook his head. "Sorry. Proves nothing about what you are, only proves what you didn't do."

"It doesn't do that," McReady sighed. "We are helpless. Because we don't know enough, and so jittery we don't think straight. Locked up! Ever watch a white corpuscle of the blood go through the wall of a blood vessel? No? It sticks out a pseudopod. And there it is--on the far side of the wall."

"Oh," said Van Wall unhappily. "The cattle tried to melt down, didn't they? They could have melted down--become just a thread of stuff and leaked under a to re-collect on the other side. Ropes--no--no, that wouldn't do it. They couldn't live in a sealed tank or--"

"If," said McReady, "you shoot it through the heart, and it doesn't die, it's a monster. That's the best test I can think of, offhand."

"No dogs," said Garry quietly, "and no cattle. It has to imitate men now. And locking up doesn't do any good. Your test might work, Mac, but I'm afraid it would be hard on the men."

Clark looked up from the galley stove as Van Wall, Barclay, McReady and Benning came in, brushing the drift from their clothes. The other men jammed into the Ad Building continued studiously to do as they were doing, playing chess, poker, reading. Ralsen was fixing a sledge on the table; Van and Norris had their heads together over magnetic data, while Harvey read tables in a low voice.

Dr. Copper snored softly on the bunk. Garry was working with Dutton over a sheaf of radio messages on the corner of Dutton's bunk and a small fraction of the radio table. Connant was using most of the table for cosmic ray sheets.

Quite plainly through the corridor, despite two closed doors, they could hear Kinner's voice. Clark banged a kettle onto the galley stove and beckoned McReady silently. The meteorologist went over to him.

"I don't mind the cooking so damn much," Clark said nervously, "but isn't there some way to stop that bird? We all agreed that it would be safe to move into Cosmos House."

"Kinner?" McReady nodded toward the door. "I'm afraid not. I can dope him, I suppose, but we don't have an unlimited supply of morphia, and he's not in danger of losing his mind. Just hysterical."

"We'll, we're in danger of losing ours. You've been out for an hour and a half. That's been going on steadily ever since, and it was going for two hours before. There's a limit, you know."

Garry wandered over slowly, apologetically. For an instant, McReady caught the feral spark of fear--horror--in Clark's eyes, and knew at the same instant it was in his own. Garry--Garry or Copper--was certainly a monster.

"If you could stop that, I think it would be a sound policy, Mac," Garry spoke quietly. "There are--tensions enough in this room. We agreed that it would be safe for Kinner in there, because everyone else in camp is under constant eyeing." Garry shivered slightly. "And try, try in God's name, to find some test that will work."

McReady sighed. "Watched or unwatched, everyone's tense. Blair's jammed the trap so it won't open now. Says he's got food enough, and keeps screaming 'Go away, go away--you're monster. I won't be absorbed. I won't. I'll tell men when they come. Go away.' So--we went away."

"There's no other test?" Garry pleaded.

McReady shrugged his shoulders. "Copper was perfectly right. The serum test could be absolutely definiteive if it hadn't been--contaminated. But that's the only dog left, and he's fixed now."

"Chemicals? Chemical tests?"

McReady shook his head. "Our chemistry isn't that good. I tried the microscope, you know."

Garry nodded. "Monster-dog and real dog were identical. But--you've got to go on. What are we going to do after dinner?"

Van Wall had joined them quietly. "Rotation sleeping. Half the crowd asleep; half awake. I wonder how many of us are monsters? All the dogs were. We thought we were safe, but somehow it got Copper--or you." Van Wall's eyes flashed uneasily. "It may have gotten every one of you--all of you but myself may be wondering, looking. No, that's not possible. You'd just spring then. I'd be helpless. We humans must somehow have the greater numbers now. But--" he stopped.

McReady laughed shortly. "You're doing what Norris complained of in me. Leaving it hanging. 'But if one more is changed--that may shift the balance of power.' It doesn't fight. I don't think it ever fights. It must be a peaceable thing, in its own--inimitable--way. It never had to, because it always gained its end--otherwise."

Van Wall's mouth twisted in a sickly grin. "You're suggesting then, that perhaps it already has the greater numbers, but is just waiting--waiting, all of them--all of you, for all I know--waiting till I, the last human, drop my wariness in sleep. Mac, did you notice their eyes, all looking at us?"

Garry sighed. "You haven't been sitting here for four straight hours, while all their eyes silently weighed the information that one of us two, Copper or I, is a monster certainly--perhaps both of us."

Clark repeated his request. "Will you stop that bird's noise? He's driving me nuts. Make him tone down, anyway."

"Still praying?" McReady asked.

"Still praying," Clark groaned. "He hasn't stopped for a second. I don't mind his praying if it relieves him, but he yells, he sings psalms and hymns and shouts prayers. He thinks God can't hear well way down here."

"Maybe He can't," Barclay grunted. "Or he'd have done something about this thing loosed from hell."

"Somebody's going to try that test you mentioned, if you don't stop him," Clark stated grimly. "I think a cleaver in the head would be as positive a test as a bullet in the heart."

"Go ahead with the food. I'll see what I can do. There may be something in the cabinets." McReady moved wearily toward the corner Copper had used as his dispensary. Three tall cabinets of rough boards, two locked, were the repostitories of the camp's medical supplies. Twelve years ago McReady had graduated, had started for an internship, and been diverted to meteorology. Copper was a picked man, a man who knew his professions thoroughly and modernly. More than half the drugs available were totally unfamiliar to McReady; many of the others he had forgotten. There was no huge medical library here, no series of journals available to learn the things that did not merit inclusion in the small library he had been forced to content himself with. Books are heavy, and every ounce of supplies had been freighted in by air.

McReady picked a barbituate hopefully. Barclay and Van Wall went with him. One man never went anywhere alone in Big Magnet.

Ralsen had his sledge put away, and the physicts had moved off the table, the poker game broken up when they got back. Clark was putting out the food. The click of spoons and the muffled sounds of eating were the only sign of life in the room. There were no words spoken as the three returned; simply all eyes focused on them questioningly, while the jaws moved methodically.

McReady stiffened suddenly. Kinner was screeching out a hymn in a hoarse, cracked voice. He looked wearily at Van Wall with a twisted grin and shook his head. "Hu-uh."

Van Wall cursed bitterly, and sat down at the table. "We'll just plumb have to take that till his voice wears out. He can't yell like that forever."

"He's got a brass throat and a cast-iron larynx," Norris declared savagely. "Then we could be hopeful, and suggest he's one of our friends. In that case he could go on renewing his throat till doomsday."

Silence clamped down. For twenty minutes they ate without a word. Then Connant jumped up with an angry violence. "You sit as still as a bunch of graven images. You don't say a word, but oh, Lord, what expressive eyes you've got. They roll around like a bunch of glass marbles spilling down a table. They wind and blink and stare--and whisper things. Can you guys look somewhere else for a change, please?

"Listen, Mac, you're in charge here. Let's run movies for the rest of the night. We've been saving those reels to make 'em last. Last for what? Who is it's going to see those last reels, eh? Let's see 'em while we can, and look at something other than each other."

"Sound idea, Connant. I, for one, am quite willing to change this in any way I can."

"Turn the sound up loud, Dutton. Maybe you can drown out the hymns," Clark suggested.

"But don't," Norris said softly, "don't turn off the lights altogether."

"The lights will be out." McReady shook his head. "We'll show all the cartoon movies we have. You won't mind seeing the old cartoons, will you?"

"Goody, goody--a moom pitcher show. I'm just in the mood." McReady turned to look at the speaker, a lean, lanky, New Englander, by the name of Caldwell. Caldwell was stuffing his pipe slowly, a sour eye cocked up to McReady.

The bronze giant was forced to laugh. "O.K., Bart, you win. Maybe we aren't quite in the mood for Popeye and trick ducks, but it's something."

"Let's play Classifications," Caldwell suggested slowly. "Or maybe you call it Guggenheim. You draw lines on a piece of paper, and put down classes of things--like animals, you know. One for 'H' and one for 'U' and so on. Like 'Human' and 'Unknown' for instance. I think that would be a hell of a lot more than movies. Maybe somebody's got a pencil that he can draw lines with, draw lines between the 'U' animals and the 'H' animals for instance."

"McReady's trying to find that kind of a pencil," Van Wall answered quietly, "but we've got three kinds of animals here, you know. One that begins with 'M.' We don't want any more."

"Mad ones, you mean. Uh-huh. Clark, I'll help you with those pans so we can get our little peep-show going." Caldwell got up slowly.

Dutton and Barclay and Benning, in charge of the projector and sound mechanism arrangements, went about their job silently, while the Ad Building was cleared and the dishes and pans disposed of. McReady drifted over toward Van Wall slowly, and leaned back in the bunk beside him. "I've been wondering, Van," he said with a wry grin, "whether or not to report my idea in advance. I forgot the 'U animals,' as Caldwell named it, could read minds. I've a vague idea of something that might work. It's too vague to bother with though. Go ahead with your show, while I try to figure out the logic of the thing. I'll take this bunk."

Van Wall glanced up, and nodded. The movie screen would be practically on a line with his bunk, hence making the pictures least distracting here, because least intelligible. "Perhaps you should tell us what you have in mind. As it is, only the unknowns know what you plan. You might be--unknown before you got it into operation."

"Won't take long, if I get it figured out right. But I don't want any more all-but-the-test-dog-monsters thing. We better move Copper into this bunk directly above me. He won't be watching the screen either." McReady nodded toward Copper's gently snoring bulk. Garry helped them lift and move the doctor.

McReady leaned back against the bunk, and sank into a trance, almost, of concentration, trying to calculate chances, operations, methods. He was scarcely aware as the others distributed themselves silently, and the screen lit up. Vaguely Kinner's hectic, shouted prayers and rasping hymn-singing annoyed him till the sound accompaniment started. The lights were turned out, but the large, light-colored areas of the screen reflected enough light for ready visibility. It made men's eyes sparkle as they moved restlessly. Kinner was still praying, shouting, his voice a raucous accompaniment to the mechanical sound. Dutton stepped up the amplification.

So long had the voice been going on, that only vaguely at first was McReady aware that something seemed missing. Lying as he was, just across the narrow room from the corridor leading to Cosmos House, Kinner's voice had reached him fairly clearly, despite the sound accompaniment of the pictures. It struck him abruptly that it had stopped.

"Dutton, cut that sound," McReady called as he sat up abruptly. The pictures flickered a moment, soundless and strangely futile in the sudden, deep silence. The rising wind on the surface above bubbled melancholy tears of sond down the stove pipes. "Kinner's stopped," McReady said softly.

"For God's sake start that sound then, he may have stopped to list," Norris snapped.

McReady rose and went down the corridor. Barclay and Van Wall left their places at the far end of the room to follow him. The flickers bulged and twisted on the back of Barclay's gray underwear as he crossed the still-functioning beam of the projector. Dutton snapped on the lights, and the pictures vanished.

Norris stood at the door as McReady had asked. Garry sat down quietly in the bunk nearest the door, forcing Clark to make room for him. Most of the others had stayed exactly where they were. Only Connant walked slowly up and down the room, in steady, unvarying rhythm.

"If you're going to do that, Connant," Clark spat, "we can get along without you altogether, whether you're human or not. Will you stop that damned rhythm?"

"Sorry." The physicist sat down in a bunk, and watched his toes thoughtfully. It was almost five minutes, five ages while the wind made the only sound, before McReady appeared at the door.

"We," he announced, "haven't got enough grief here already. Somebody's tried to help us out. Kinner has a knife in his throat, which was why he stopped singing, probably. We've got monsters, madmen and murderers. Any more 'M's' you can think of, Caldwell? If there are, we'll probably have 'em before long."

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