In science-fiction, as in all categories of fiction, there are stories that are so outstanding from the standpoint of characterization, concept, and background development that they remain popular for decades. Two such stories were Murray Leinster's The Mad Planet and Red Dust. Originally published in 1923, they have been reprinted frequently both here and abroad. They are now scheduled for book publication. Especially for this magazine, Murray Leinster has written the final story in the series. It is not necessary to have read the previous stories to enjoy this one. Once again, Burl experiences magnificent adventures against a colorful background, but to the whole the author has added philosophical and psychological observations that give this story a flavor seldom achieved in science-fiction.

Under his real name of Will Fitzgerald Jenkins, the author has sold to The Saturday Evening Post, Colliers', Today's Woman, in fact every important publication in America. He has had over 1200 stories published, 15 books and 35 science-fiction stories anthologized. His writing earned him a listing in Who's Who in America.

The Directory-ship Tethys made the first landing on the planet, L216¹². It was a goodly world, with an ample atmosphere and many seas, which the nearby sun warmed so lavishly that a perpetual cloud-bank hid them and all the solid ground from view. It had mountains and islands and high plateaus. It had day and night and rain. It had an equable climate, rather on the tropical side. But it possessed no life.

No animals roamed its solid surface. No vegetation grew from its rocks. Not even bacteria struggled with the stones to turn them into soil. No living thing, however small, swam in its oceans. It was one of that disappointing vast majority of otherwise admirable worlds which was unsuited for colonization solely because it had not been colonized before. It could be used for biological experiments in a completely germ-free environment, or ships could land upon it for water and supplies of air. The water was pure and the air breathable, but it had no other present utility. Such was the case with an overwhelming number of Earth-type planets when first discovered in the exploration of the galaxy. Life simply hadn't started there.

So the ship which first landed upon it made due note for the Galactic Directory and went away, and no other ship came near the planet for eight hundred years.

But nearly a millennium later, the Seed-Ship Orana arrived. It landed and carefully seeded the useless world. It circled endlessly above the clouds, dribbling out a fine dust comprised of the spores of every conceivable microorganism that could break down rock to powder and turn the powder to organic matter. It also seeded with moulds and fungi and lichens, and everything that could turn powdery primitive soil into stuff on which higher forms of life could grow. The Orana seeded the seas with plankton. Then it, too, went away.

Centuries passed. Then the Ecological Preparation Ship Ludred swam to the planet from space. It was a gigantic ship of highly improbable construction and purpose. It found the previous seeding successful. Now there was soil which swarmed with minute living things. There were fungi which throve monstrously. The seas stank of teeming minuscule life-forms. There were even some novelties on land, developed by strictly local conditions. There were, for example, paramecium as big as grapes, and yeasts had increased in size so that they bore flowers visible to the naked eye. The life on the planet was not aboriginal, though. It had all been planted by the seed-ship of centuries before.

The Ludred released insects, it dumped fish into the seas. It scattered plant-seeds over the continents. It treated the planet to a sort of Russell's Mixture of living things. The real Russell's Mixture is that blend of simple elements in the proportions found in suns. This was a blend of living creatures, of whom some should certainly survive by consuming the now habituated flora, and others which should survive by preying on the first. The planet was stocked, in effect, with everything it could be hoped might live there.

But at the time of the Ludred's visit of course no creature needing parental care had any chance of survival. Everything had to be able to care for itself the instant it burst its egg. So there were no birds or mammals. Trees and plants of divers sorts, and fish and crustaceans and insects could be planted. Nothing else.

The Ludred swam away through emptiness.

There should have been another planting, centuries later still, but it was never made. When the Ecological Preparation Service was moved to Algol IV, a file was upset. The cards in it were picked up and replaced, but one was missed. So that planet was forgotten. It circled its sun in emptiness. Cloud-banks covered it from pole to pole. There were hazy markings in certain places, where high plateaus penetrated the clouds. But from space the planet was featureless. Seen from afar, it was merely a round white ball—white from its cloud-banks and nothing else.

But on its surface, in its lowlands it was nightmare.

Especially was it nightmare—after some centuries—for the descendants of the human beings from the space-liner Icarus, wrecked there some forty-odd generations ago. Naturally, nobody anywhere else thought of the Icarus any more. It was not even remembered by the descendants of its human cargo, who now inhabited the planet. The wreckage of the ship was long since hidden under the seething, furiously striving fungi of the boil. The human beings on the planet had forgotten not only the ship but very nearly everything—how they came to this world, the use of metals, the existence of fire, and even the fact that there was such a thing as sunlight. They lived in the lowlands, deep under the cloud-bank, amid surroundings which were riotous, swarming, frenzied horror. They had become savages. They were less than savages. They had forgotten their high destiny as men.

Dawn came. Grayness appeared overhead and increased. That was all. The sky was a blank, colorless pall, merely mottled where the clouds clustered a little thicker or a little thinner, as clouds do. But the landscape was variegated enough! Where the little group of people huddled together, there was a wide valley. Its walls rose up and up into the very clouds. The people had never climbed those hillsides.

They had not even traditions of what might lie above them, and their lives had been much too occupied to allow of speculations on cosmology. By day they were utterly absorbed in two problems which filled every waking minute. One was the securing of food to eat, under the conditions of the second problem, which was that of merely staying alive.

There was only one of their number who sometimes thought of other matters, and he did so because he had become lost from his group of humans once, and had found his way back to it. His name was Burl, and his becoming lost was pure fantastic accident, and his utilization of a fully inherited power to think was the result of extraordinary events. But he still had not the actual habit of thinking. This morning he was like his fellows.

All of them were soaked with wetness. During the night—every night—the sky dripped slow, spaced, solemn water-drops during the whole of the dark hours. This was customary. But normally the humans hid in the mushroom-forests, sheltered by the toadstools which now grew to three man-heights. They denned in small openings in the tangled mass of parasitic growths which flourished in such thickets. But this last night they had camped in the open. They had no proper habitations of their own. Caves would have been desirable, but insects made use of caves, and the descendants of insects introduced untold centuries before had shared in the size-increase of paramecium and yeasts and the few true plants which had been able to hold their own. Mining-wasps were two yards long, and bumble-bees were nearly as huge, and there were other armored monstrosities which also preferred caves for their own purposes. And of course the humans could not build habitations, because anything men built to serve the purpose of a cave would instantly be preempted by creatures who would automatically destroy any previous occupants.

The humans had no fixed dens at any time. Now they had not even shelter. They lacked other things, also. They had no tools save salvaged scraps of insect-armor—great sawtoothed mandibles or razor-pointed leg-shells—which they used to pry apart the edible fungi on which they lived, or to get at the morsels of meat left behind when the brainless lords of this planet devoured each other. They had not even any useful knowledge, except desperately accurate special knowledge of the manners and customs of the insects they could not defy. And on this special morning they concluded that they were doomed. They were going to be killed. They stood shivering in the open, waiting for it to happen.

It was not exactly news. They had had warning days ago, but they could do nothing about it. Their home valley, to be sure, would have made any civilized human being shudder merely to look at it, but they had considered it almost paradise. It was many miles long, and a fair number wide, and a stream ran down its middle. At the lower end of the valley there was a vast swamp, from which at nightfall the thunderously deep-bass croaking of giant frogs could be heard. But that swamp had kept out the more terrifying creatures of that world. The thirty-foot centipedes could not cross it or did not choose to. The mastodon-sized tarantulas which ravaged so much of the planet would not cross it save in pursuit of prey. So the valley was nearly a haven of safety.

True, there was one clotho spider in its ogre's castle nearby, and there was a labyrinth spider in a minor valley which nobody had ever ventured into, and there were some—not many—praying-mantises as tall as giraffes. They wandered terribly here and there. But most members of insect life here were absorbed in their own affairs and ignored the humans. There was an ant-city, whose foot-long warriors competed with the humans as scavengers. There were the bees, trying to eke out a livelihood from the great, cruciform flowers of the giant cabbage-plants and the milkweeds when water-lilies in the swamps did not bear their four-foot blooms. Wasps sought their own prey. Flies were consumers of corruption, but even the flies two feet in length would shy away from a man who waved his arms at it. So this valley had seemed to these people to be a truly admirable place.

But a fiend had entered it. As the gray light grew stronger the shivering folk looked terrifiedly about them. There were only twenty of the people now. Two weeks before there had been thirty. In a matter of days or less, there would be none. Because the valley had been invaded by a great gray furry spider!

There was a stirring, not far from where the man-folk trembled. Small, inquisitive antennae popped into view among a mass of large-sized pebbles. There was a violent stirring, and gravel disappeared. Small black things thrust upward into view and scurried anxiously about. They returned to the spot from which they had emerged. They were ants, opening the shaft of their city after scouting for danger outside. They scratched and pulled and tugged at the plug of stones. They opened the ant-city's artery of commerce. Strings of small black things came pouring out. They averaged a foot in length, and they marched off in groups upon their divers errands. Presently a group of huge-jawed soldier-ants appeared, picking their way stolidly out of the opening. They waited stupidly for the workers they were to guard. The workers came, each carrying a faintly greenish blob of living matter. The caravan moved off. The humans knew exactly what it was. The green blobs were aphids—plant lice: ant-cows—small creatures sheltered and guarded by the ants and daily carried to nearby vegetation to feed upon its sap and yield inestimable honeydew.

Something reared up two hundred yards away, where the thin mist that lay everywhere just barely began to fade all colorings before it dimmed all outlines. The object was slender. It had a curiously humanlike head. It held out horrible sawtoothed arms in a gesture as of benediction—which was purest mockery. Something smaller was drawing near to it. The colossal praying mantis held its pose, immovable. Presently it struck downward with lightning speed. There was a cry. The mantis rose erect again, its great arms holding something that stirred and struggled helplessly, and repented its unconsonanted outcry. The mantis ate it daintily as it struggled and screamed.

The humans did not watch this tragedy. The mantis would eat a man, of course. It had. The only creatures immune to its menace were ants, which for some reason it would not touch. But it was a mantis' custom after spotting its prey to wait immobile for the unlucky creature to come within its reach. It preferred to make its captures that way. Only if a thing fled did the mantis pursue with deadly ferocity. Even then it dined with monstrous deliberation as this one dined now. Still, mantises could be seen from a distance and hidden from. They were not the terror which had driven the humans even from their hiding-places.

It had been two weeks since the giant hunting-spider had come through a mountain pass into this valley to prey upon the life within it. It was gigantic even of its kind. It was deadliness beyond compare. The first human to see it froze in terror. It was disaster itself. Its legs spanned yards. Its fangs were needle-sharp and feet in length—and poisoned. Its eyes glittered with insatiable, insane blood-lust. Its coming was ten times more deadly to the unarmed folk than a Bengal tiger loose in the valley would have been.

It killed a man the very first day it was in the valley, leaving his sucked-dry carcass, and going on to destroy a rhinoceros-beetle and a cricket—whose deep-bass cries were horrible—and proceeded down the valley, leaving only death behind it. It had killed other men and women since. It had caught four children. But even that was not the worst. It carried worse, more deadly, more inevitable disaster with it.

Because, bumping and bouncing behind its abdomen as it moved, fastened to its body with cables of coarse and discolored silk, the hunting-spider dragged a burden which was its own ferocity many times multiplied. It dragged an egg-bag. The bag was larger than its body, four feet in diameter. The female spider would carry this burden—cherishing it—until the eggs hatched. Then there would be four to five hundred small monsters at large in the valley. And from the instant of their hatching they would be just such demoniac creatures as their parents. They would be small, to be sure. Their legs would span no more than a foot. Their bodies would be the size of a man's fist. But they could leap two yards, instantly they reached the open air, and their inch-long fangs would be no less envenomed, and their ferocity would be in madness, in insanity and in stark maniacal horror equal the great gray fiend which had begot them.

The eggs had hatched. Today—now—this morning—they were abroad. The little group of humans no longer hid in the mushroom-forests because the small hunting-spiders sought frenziedly there for things to kill. Hundreds of small lunatic demons roamed the valley. They swarmed among the huge toadstools, killing and devouring all living things large and small. When they encountered each other they fought in slavering, panting fury, and the survivors of such duels dined upon their brothers. Small truffle-beetles died, clicking futilely. Infinitesimal grubs, newly hatched from butterfly eggs and barely six inches long, furnished them with tidbits. But they would kill anything and feast upon it.

A woman had died yesterday, and two small gray devils battled murderously above her corpse.

Just before darkness a huge yellow butterfly had flung itself agonizedly aloft, with these small dark horrors clinging to its body, feasting upon the juices of the body their poison had not yet done to death.

And now, at daybreak, the humans looked about despairingly for their own deaths to come to them. They had spent the night in the open lest they be trapped in the very forests that had been their protection. Now they remained in clear view of the large gray murderer should it pass that way. They did not dare to hide because of that ogreish creature's young, who panted in their blood-lust as they scurried here and there and everywhere.

As the day became established, the clouds were gray—gray only. The night-mist thinned. One of the younger women of the tribe—a girl called Saya—saw the huge thing far away. She cried out, choking. The others saw the monster as it leaped upon and murdered a vividly colored caterpillar on a milkweed near the limit of vision. The milkweed was the size of a tree. The caterpillar was four yards long. While the enormous victim writhed as it died, not one of the humans looked away. Presently all was still. The hunting-spider crouched over its victim in obscene absorption. Having been madness incarnate, it now was the very exemplar of a horrid gluttony.

Again the humans shivered. They were without shelter. They were without even the concept of arms. But it was morning, and they were alive, and therefore they were hungry. Their desperation was absolute, but desperation to some degree was part of their lives. Yet they shivered and suffered. There were edible mushrooms nearby, but with the deadly small replicas of the hunting-spider giant roaming everywhere, any movement was as likely to be deadly as standing still to be found and killed. The humans murmured to one another, fearfully.

But there was the young man called Burl, who had been lost from his tribe and had found it again. The experience had changed him. He had felt stirrings of atavistic impulses in recent weeks—the more especially when the young girl Saya looked at him. It was not normal, in humans conditioned to survive by flight, that Burl should feel previously unimagined hunger for fury—a longing to hate and do battle. Of course men sometimes fought for a particular woman's favor, but not when there were deadly insects about. The carnivorous insects were not only peril, but horror unfaceable. So Burl's sensations were very strange. On this planet a courtship did not usually involve displays of valor. A man who was a more skillful forager than the foot-long ants was an acceptable husband. Warriors did not exist.

Burl did not even know what a warrior was. Yet today the sullen, unreasonable impulses to conduct what he could not quite imagine were very strong. He knew all the despairing terror the others felt. But he also was hungry. The sheer doom that was upon his group did not change the fact that he wanted to eat, nor did it change the fact that he felt queer when the girl Saya looked at him. Because she was terrified, the same sort of atavistic process was at work in her. She looked to Burl. Men no longer served as protectors against enemies so irresistible as giant spiders. It was not possible. But when Burl realized her regard his chest swelled. He felt a half-formed impulse to beat upon it. His new-found reasoning processes told him that this particular fear was different in some fashion from the terrors men normally experienced. It was. This was a different sort of emergency. Most dangers were sudden and either immediately fatal or somehow avoidable. This was different. There was time to savor its meaning and its hopelessness. It seemed as if it should be possible to do something about it. But Burl was not able, as yet, to think what to do. The bare idea of doing anything was unusual, now. Because of it, though, Burl was able to disregard his terror when Saya regarded him yearningly.

The other men muttered to each other of the sudden death in the mushroom thickets. No less certain death now feasted on the dead yellow caterpillar. But Burl abruptly pushed his way clear of the small crowd and scowled for Saya to see. He moved toward the nearest fungus-thicket. An edible mushroom grew at its very edge. He marched toward it, swaggering. Men did not often swagger on this planet.

But then he ceased to swagger. His approach to the mingled mass of toadstools and lesser monstrosities grew slower. His feet dragged. He came to a halt. His impulse to combat conflicted with the facts of here and now. His flesh crawled at the thought of the grisly small beasts which now might be within yards. These thickets had been men's safest hiding-places. Now they were places of surest disaster.

He stopped, with a coldness at the pit of his stomach. But as it was a new experience to be able to have danger come in a form which could be foreseen, so Burl now had a new experience in that he was ashamed to be afraid. Somehow, having tacitly undertaken to get food for his companions, he could not bring himself to draw back while they watched. But he did want desperately to get the food in a hurry and get away from there.

He saw a gruesome fragment of a tragedy of days before. It was the emptied, scraped, hollow leg-shell of a beetle. It was horrendously barbed. Great, knife-edged spines lined its edge. They were six inches in length. And men did not have weapons any more, but they sometimes used just such objects as this to dismember defenseless giant slugs they came upon.

Burl picked up the hollow shell of the leg-joint. He shook it free of clinging moulds—and small things an inch or two in length dropped from it and scurried frantically into hiding. He moved hesitantly toward the edible mushroom which would be food for Saya and the rest. He was four yards from the thicket. Three. Two. He needed to move only six feet, and then slice at the flabby mushroom-head, and he would be at least an admirable person in the eyes of Saya.

Then he cried out thinly. Something small, with insane eyes, leaped upon him from the edge of a giant toadstool.

It was, of course, one of the small beasts which had hatched from the hunting-spider's egg-bag. It had grown. Its legs now spanned sixteen inches. Its body was as large as Burl's two fists together. It was big enough to enclose his head in a cage of loathesomeness formed by its legs, while its fangs tore at his scalp. Or it could cover his chest with its abominableness while its poison filled his veins, and while it feasted upon him afterward....

He flung up his hands in a paralytic, horror-stricken attempt to ward it off. But they were clenched. His right hand did not let go of the leg-section with its razor-sharp barbs.

The spider struck the beetle-leg. He felt the impact. Then he heard gaspings and bubblings of fury. He heard an indescribable cry which was madness itself. The chitinous object he had picked up now shook and quivered of itself.

The spider was impaled. Two of its legs were severed and twitched upon the ground before him. Its body was slashed nearly in half. It writhed and struggled and made beastly sounds. Thin, colored fluids dripped from it. A disgusting musky smell filled the air. It strove to reach and kill him as it died. Its eyes looked like flames.

Burl's arm shook convulsively. The small thing dropped to the ground. Its remaining legs moved frantically but without purpose.

It died, though its leg continued to twitch and stir and quiver.

Burl remained frozen, for seconds. It was an acquired instinct; a conditioned reflex which humans had to develop on this world. When danger was past, one stayed desperately still lest it return. But Burl's thoughts were now not of horror but a vast astonishment. He had killed a spider! He had killed a thing which would have killed him! He was still alive!

And then, being a savage, and an animal, as well as a human being, he acted according to that highly complicated nature. As a savage, he knew with strict practicality that it was improbable that there was another baby spider nearby. If there had been, they would have fought each other. As an animal, he was again hungry. As a human being, he was vain.

So he moved closer to the toadstool-thicket and put his hand out and broke off a great mass of the one edible mushroom at the edge. A noisesome broth poured out and little maggots dropped to the ground and writhed there in it. But most of what he had broken off was sound. He turned to take it to Saya. Then he saw the dropped weapon and the spider. He picked up the weapon.

The spider's legs still twitched, though futilely. He spiked the small body on the beetle-leg's spines. He strode back to the remnant of his tribe with a peculiar gait that even he had not often practiced.

It was rather more pronounced than a swagger. It was a strut.

They trembled when they saw the dead creature he had killed. He gave Saya the food. She took it, looking at him with bright and intense eyes. He took a part of the mushroom for himself and ate it, scowling. Thoughts were struggling to form in his mind. He was not accustomed to thinking, but he had done more of it than any other of the pitiful group about him.

He felt eyes watching him. There were five adult men in this group besides himself, and six women. The rest were children, from gangling adolescents to one mere infant in arms. They were a remarkably colorful group at the moment, had he only known it. The men wore yellow-and-gold-brown loin-cloths of caterpillar-fur, stripped from the drained carcasses of creatures that the formerly resident clothed spider had killed. The women wore cloaks of butterfly-wing, similarly salvaged from the remnants of a meal left unfinished by a finicky or engorged praying mantis. The stuff was thick and leathery, but it was magnificently tinted in purples and yellows.

Time passed. The mushroom Burl had brought was finished. Some eyes always explored the clear ground around this group. But other eyes fixed themselves upon Burl. It was not a consciously questioning gaze. It was surely not a hopeful one. But men and women and children looked at him. They marveled at him. He had dared to go and get food! He had been attacked by one of the creatures who doomed them all, but he was not dead! Instead, he had killed the spider! It was marvelous! It was unparalleled that a man should kill anything that attacked him!

The doomed small group regarded Burl with wondering eyes. He brushed his hands together. He looked at Saya. He wished to be alone with her. He wished to know what she thought when she looked at him. Why she looked at him. What she felt when she looked at him.

He stood up and said dourly:

"Come!"

She moved timidly and gave him her hand. He moved away. There was but one way that any human being on this planet would think to move, from this particular spot just now—away from the still-feasting gigantic horror whose offspring he had killed. The folk shivered near the edge of the first upward slope of the valley wall. Burl moved in that direction. Toward the slope. Saya went with him.

Before they had gone ten yards a man spoke to his wife. They followed Burl, with their three children. Five yards more, and two of the remaining three adult men were hustling their families in his wake also. In seconds the last was in motion.

Burl moved on, unconscious of any who followed him, aware only of Saya. The procession, absurd as it was, continued in his wake simply because it had begun to do so. A skinny, half-grown boy regarded Burl's stained weapon. He saw something half-buried in the soil and moved aside to tug at it. It was part of the armor of a former rhinoceros-beetle. He went on, rather awkwardly holding a weapon which might have been called a dagger, eighteen inches long, except that no dagger would have a hand-guard nearly its own length in diameter.

They passed a struggling milkweed plant, no more than twenty feet high and already scabrous with scale and rusts upon its lower parts. Ants marched up and down its stalk in a steady, single file, placing aphids from the ant-city on suitable spots to feed, and to multiply as only parthenogenic aphids can do. But already on the far side of the milkweed, an ant-lion climbed up to do murder among them. The ant-lion was the larval form the lace-wing fly, of course. Aphids were its predestined prey.