On the first night of its roaming, nothing in particular happened. The explorer became completely familiar with the way the controls of the machine worked. As a machine, of course, it was vastly more powerful than an animal. It could make leaps no mere creature of flesh and blood could duplicate; its balancing devices were admirable; it was, naturally, immune to fatigue. The Qul-En inside it was pleased with the job.

  That night Antonio and Salazar bedded down their sheep in a natural amphitheatre and Antonio slept heavily, snoring. He was a highly superstitious ancient, so he wore various charms of a quasi-religious nature. Salazar merely turned around three times and went to sleep. But while the man slept soundly, Salazar woke often. Once he waked sharply at a startled squawking among the lambs. He got up and trotted over to make sure that everything was all right, sniffed the air suspiciously. Then he went back, scratched where a flea had bitten him, bit—nibbling—at a place his paws could not reach, and went back to sleep. At midnight he made a clear circle around his flock and went back to slumber with satisfaction. Toward dawn he raised his head suspiciously at the sound of a coyote’s howl, but the howl was far away Salazar dozed until daybreak, when he rose, shook himself, stretched himself elaborately, scratched thoroughly, and was ready for a new day. The man waked, wheezing, and cooked breakfast; it appeared that the normal order of things would go undisturbed.

  For a time it did; there was certainly no disturbance at the ship. The small silvery vessel was safely hidden. There was a tiny, flickering light inside—the size of a pin-point—which wavered and changed color constantly where a sort of tape unrolled before it. It was a recording device, making note of everything the roaming pseudo-mountain lion’s eyes saw and everything its microphonic ears listened to. There was a bank of air-purifying chemical which proceeded to regenerate itself by means of air entering through a small ventilating slot. It got rid of carbon dioxide and stored up oxygen in its place, in readiness for further voyaging.

  Of course, ants exploded the whole outside of the space-vessel, and some went inside through the ventilator-opening. They began to cart off some interesting if novel foodstuff they found within. Some very tiny beetles came exploring, and one variety found the air-purifying chemical refreshing. Numbers of that sort of beetle moved in and began to raise large families. A minuscule moth, too, dropped eggs lavishly in the nest-like space in which the Qul-En explorer normally reposed during space-flight. But nothing really happened.

  Not until late morning. It was two hours after breakfast-time when Salazar found traces of the mountain lion which was not a mountain lion. He found a rabbit that had been killed. Having been killed, it had very carefully been opened up, its various internal organs spread out for examination, and its nervous system traced in detail. Its brain-tissue, particularly, had been most painstakingly dissected, so the amount of a certain complex hormone to be found in it could be calculated with precision. The Qul-En in the lion shape had been vastly pleased to find the sought-for hormone in another animal besides a mountain lion.

  The dissection job was a perfect anatomical demonstration; no instructor in anatomy could have done better, and few neuro-surgeons could have done as well with the brain. It was, in fact, a perfect laboratory job done on a flat rock in the middle of a sheep-range, and duly reproduced on tape by a flickering, color-changing light. The reproduction, however, was not as good as it should have been, because the tape was then covered by small ants who had found its coating palatable and were trying to clean it off.

  Salazar saw the rabbit. There were blow-flies buzzing about it, and a buzzard was reluctantly flying away because of his approach. Salazar barked at the buzzard. Antonio heard the barking; he came.

  Antonio was ancient, superstitious, and unwashed. He came wheezing, accompanied by flies who had not finished breakfasting on the bits of his morning meal he had dropped on his vest. Salazar wagged his tail and barked at the buzzard. The rabbit had been neatly dissected, but not eaten. The cuts which opened it up were those of a knife or scalpel. It was not—it was definitely not!—the work of an animal. But there were mountain-lion tracks, and nothing else. More, every one of the tracks was that of a hind foot! A true mountain lion eats what he catches; he does not stand on his hind-paws and dissect it with scientific precision. Nothing earthly had done this!

  Antonio’s eyes bulged out. He thought instantly of magic, Black Magic. He could not imagine dissection in the spirit of scientific inquiry; to him, anything that killed and then acted in this fashion could only come from the devil.

  He gasped and fled, squawking. When he had run a good hundred yards, Salazar caught up to him, very much astonished. He overtook his master and went on ahead to see what had scared the man so. He made casts to right and left, then went in a conscientious circle all around the flock under his care. Presently he came back to Antonio, his tongue lolling out, to assure him that everything was all right. But Antonio was packing, with shaking hands and a sweat-streaked brow.

  In no case is the neighborhood of a mountain lion desirable for a man with a flock of sheep. But this was no ordinary mountain lion. Why, Salazar—honest, stout-hearted Salazar— did not scent a mountain lion in those tracks. He would have mentioned it vociferously if he had, so this was beyond nature. The lion was un fantasmo or worse; Antonio’s thoughts ran to were-tigers, ghosts-lions, and sheer Indian devils. He packed, while Salazar scratched fleas and wondered what was the matter.

  They got the flock on the move. The sheep made idiotic efforts to disperse and feed placidly where they were. Salazar rounded them up and drove them on. It was hard work, but even Antonio helped in frantic energy—which was unusual.

  Near noon, four miles from their former grazing-ground, there were mountain-peaks all around them. Some were snowcapped, and there were vistas of illimitable distance everywhere. It was very beautiful indeed, but Antonio did not notice; Salazar came upon buzzards again. He chased them with loud barkings from the meal they reluctantly shared with blowflies and ants. This time it wasn’t a rabbit; it was a coyote. It had been killed and most painstakingly taken apart to provide at a glance all significant information about the genus canis, species latrans, in the person of an adult male coyote. It was a most enlightening exhibit; it proved conclusively that there was a third type of animal, structurally different from both mountain lions and rabbits, which had the same general type of nervous system, with a mass of nerve-tissue in one large mass in a skull, which nerve-tissue contained the same high percentage of the desired hormone as the previous specimens. Had it been recorded by a tiny colored flame in the hidden ship —the flame was now being much admired by small red bugs and tiny spiders—it would have been proof that the Qul-En would find ample supplies on Earth of the complex hormone on which the welfare of their race now depended. Some members of the Qul-En race, indeed, would have looked no farther. But sampling which involved only three separate species and gave no proof of their frequency was not quite enough; the being in the synthetic mountain lion was off in search of further evidence.

  Antonio was hardly equipped to guess at anything of this sort. Salazar led him to the coyote carcass; it had been neatly halved down the breastbone. One half the carcass had been left intact; the other half was completely anatomized, and the brain had been beautifully dissected and spread out for measurement. Antonio realized that intelligence had been at work. But—again—he saw only the pad-tracks of a mountain lion, and he was literally paralyzed by horror.

  Antonio was scared enough to be galvanized into unbelievable energy. He would have fled gibbering to Ensenada Springs, some forty miles as the crow flies, but to flee would be doom itself. The devils who did this sort of work liked—he knew— to spring upon a man alone. But they can be fooled.

  The Qul-En in the artificial mountain lion was elated. To the last quivering appendage on the least small tentacle of its body, the pilot of the facsimile animal was satisfied. It had found good evidence that the desired nervous system and concentration of the desired hormone in a single mass of nerve-tissue was normal on this planet! The vast majority of animals should have it. Even the local civilized race might have skulls with brains in them, and, from the cities observed from the stratosphere, that race might be the most numerous fair-sized animal on the planet!

  It was to be hoped for, because large quantities of the sought-for hormone were needed; taking specimens from cities would be most convenient. Long-continued existence under the artificial conditions of civilization—a hundred thousand years of it, no less—had brought about exhaustion of the Qul-Ens’ ability to create all their needed hormones in their own bodies. Tragedy awaited the race unless the most critically needed substance was found. But now it had been!

  Antonio saw it an hour later, and wanted to shriek; it looked exactly like a mountain lion, but he knew it was not flesh and blood because it moved in impossible bounds. No natural creature could leap sixty feet; the mountain-lion shape did. But it was convincingly like its prototype to the eye. It stopped, and regarded the flock of sheep, made soaring progression to the front of the flock, and came back again. Salazar ignored it. Neither he nor the sheep scented carnivorous animal life. Antonio hysterically concluded that it was invisible to them; he began an elaborate, lunatic pattern of behavior to convince it that magic was at work against it, too.

  He began to babble to his sheep with infinite politeness, spoke to blank-eyed creatures as Senor Gomez and Senora Onate. He chatted feverishly with a wicked-eyed ram, whom he called Senor Guttierez. A clumsy, wabbling lamb almost upset him, and he scolded the infant sheep as Pepito. He lifted his hat with great gallantry to a swollen ewe, hailing her as Senora Garcia, and observed in a quavering voice that the flies were very bad today. He moved about in his flock, turning the direction of its march and acting as if surrounded by a crowd of human beings. This should at least confuse the devil whom he saw. And while he chatted with seeming joviality, the sweat poured down his face in streams.

  Salazar took no part in this deception. The sheep were fairly docile, once started; he was able to pause occasionally to scratch, and once even to do a luxurious, thorough job on that place in his back between his hind legs which is so difficult to reach. There was only one time when he had any difficulty. That was when there was a sort of eddying of the sheep, ahead. There were signs of panic. Salazar went trotting to the spot. He found sheep milling stupidly, and rams pawing the ground defying they had no idea what. Salazar found a deer-carcass on the ground and the smell of fresh blood in the air and the sheep upset because of it. He drove them on past, barking where barking would serve and nipping flanks where necessary—afterward disgustedly tonguing bits of wool out of his mouth.

  The sheep went on. But Antonio, when he came to the deer-carcass, went icy-cold in the most exquisite of terror; the deer had been killed by a mountain lion—there were tracks about. Then it, too, had been cut into as if by a dissector’s scalpel, but the job was incomplete. Actually, the pseudo-mountain lion had been interrupted by the approach of the flock. There were hardly blow-flies on the spot as yet. Antonio came to it as he chatted insanely with a sheep with sore eyes and a halo of midges about its head, whom he addressed as Senorita Carmen. But when he saw the deer his throat clicked shut. He was speechless.

  To pass a creature laid out for magical ceremony was doom indubitable, but Antonio acted from pure desperation. He recited charms which were stark paganism and would involve a heavy penance when next he went to confession. He performed other actions, equally deplorable; when he went on, the deer was quite spoiled for neat demonstration of the skeletal, circulatory, muscular and especially the nervous system and brain-structure of genus cervus, species dama, specimen and adult doe. Antonio had piled over the deer all the brush within reach, had poured over it the kerosene he had for his night-lantern, and had set fire to the heap with incantations that made it a wholly impious sacrifice to quite nonexistent heathen demons.

  Salazar, trotting back to the front of the flock after checking on Antonio and the rear-guard, wrinkled his nose and sneezed as he went past the blaze again. Antonio tottered on after him. But Antonio’s impiety had done no good. The tawny shape bounded back into sight among the boulders on the hillside, It leaped with infinite grace for impossible distances. Naturally! No animal can be as powerful as a machine, and the counterfeit mountain lion was a machine vastly better than men could make.

  The Qul-En now zestfully regarded the flock of sheep. It looked upon Salazar and Antonio with no less interest. The Qul-En explorer was an anatomist and organic chemist rather than a zoologist proper, but it guessed that the dog was probably a scavenger and that the man had some symbiotic relationship to the flock.

  Salazar, the dog, was done a grave injustice in that estimate. Even Antonio was given less than he deserved. Now he was gray with horror. The blood in his veins turned to ice as he saw the false mountain lion bounding back upon the hillside. No normal wild creature would display itself so openly. Antonio considered himself both doomed and damned; stark despair filled him. But with shaking hands and no hope at all, he carved a deep cross on the point of a bullet for his ancient rifle. Licking his lips, he made similar incisions on other bullets in reserve.

  The Qul-En vehicle halted. The flock had been counted; now to select specimens and get to work. There were six new animal types to be dissected for the nervous organ yielding the looked-for hormone. Four kinds of sheep—male and female, and adult and immature of each kind—the biped, and the dog. Then a swift survey to estimate the probable total number of such animals, available, and—

  Antonio saw that the devil mountain lion was still. He got down on one knee, fervently crossed himself and fed a cross-marked bullet into the chamber of his rifle. He lined up the sights on the unearthly creature. The lion-facsimile watched him interestedly; the sight of a rifle meant nothing to the Qul-En, naturally. But the kneeling posture of the man was strange. It was part, perhaps, of the pattern of conduct which had led him to start that oxidation process about the deer-specimen.

  Antonio fired. His hands trembled and the rifle shook; nothing happened. He fired again and again, gasping in his fear. And he missed every time.

  The cross-marked bullets crashed into red earth and splashed from naked rock all about the Qul-En vehicle. When sparks spat from a flint pebble, the pilot of the mountain lion realized that there was actual danger here. It could have slaughtered man and dog and sheep by the quiver of a tentacle, but that would have ruined them as specimens. To avoid spoiling specimens it intended to take later, the Qul-En put the mountain-lion shape into a single, magnificent leap. It soared more than a hundred feet up-hill and over the crest at its top; then it was gone.

  Salazar ran barking after the thing at which Antonio had fired, sniffed at the place from which it had taken off. There was no animal smell there at all. He sneezed, and then trotted down again. Antonio lay flat on the ground, his eyes hidden, babbling. He had seen irrefutable proof that the shape of the mountain lion was actually a fiend from hell.

  *

  Behind the hill-crest, the Qul-En moved away. It had not given up its plan of selecting specimens from the flock, of course, nor of anatomizing the man and dog. It was genuinely interested, too, in the biped’s novel method of defense. It dictated its own version of the problems raised, on a tight beam to the wavering, color-changing flame. Why did not the biped prey on the sheep if it could kill them? What was the symbiotic relationship of the dog to the man and the sheep? The three varieties of animal associated freely. The Qul-En dictated absorbed speculations, then it hunted for other specimens. It found a lobo wolf, and killed it, verified that this creature also could be a source of hormones. It slaughtered a chipmunk and made a cursory examination. Its ray-beam had pretty well destroyed the creature’s brain-tissue, but by analogy of structure this should be a source also.

  In conclusion, the Qul-En made a note via the wavering pinpoint of flame that the existence of a hormone-bearing nervous system, centralized in a single mass of hormone-bearing nerve-tissue inside a bony structure, seemed universal among the animals of this planet. Therefore it would merely examine the four other types of large animal it had. discovered, and take off to present its findings to the Center of its race. With a modification of the ray-beam to kill specimens without destroying the desired hormone, the Qul-En could unquestionably secure as much as the race could possibly need. Concentrations of the local civilized race in cities should make large-scale collection of the hormone practical unless that civilized race was an exception to the general nervous structure of all animals so far observed.

  This was dictated to the pin-point flame, and the flame faithfully wavered and changed color to make the record. But the tape did not record it; a rather large beetle had jammed the tape-reel. It was squashed in the process, but it effectively messed up the recording apparatus. Even before the tape stopped moving, though, the record had become defective; tiny spiders had spun webs, earwigs got themselves caught. The flame, actually, throbbed and pulsed restlessly in a cobwebby coating of gossamer and tiny insects. Silverfish were established in the plastic lining of the Qul-En ship; beetles multiplied enormously in the air-refresher chemical; moth-larvae already gorged themselves on the nest-material of the intrepid explorer outside. Ants were busy on the food-stores. Mites crawled into the ship to prey on their larger fellows, and a praying-mantis or so had entered to eat their smaller ones. There was an infinite number of infinitesimal flying things dancing in the dark; large spiders busily spun webs to snare them, and flies of various sorts were attracted by odors coming out of the ventilator-opening, and centipedes rippled sinuously inside—

  Night fell upon the world. The pseudo-mountain lion roamed the wild, keeping in touch with the tide of baa-ing sheep now headed for the lowlands. It captured a field-mouse and verified the amazing variety of planetary forms containing brain-tissue rich in hormones. But the sheep-flock could not be driven at night. When stars came out, to move them farther became impossible. The Qul-En returned to select its specimens in the dark, with due care not to allow the man to use his strange means of defense. It found the flock bedded down.