MacAloon rose in the stirrups of his saddle-lizard. His guide, a Venusian fishman, trembled nervously at the mount's side and pointed straight ahead. MacAloon followed the direction of the quivering four-jointed, scaly arm.

"See, bossmac?" the reptilian native hissed in fright. "Bosslimpy speak truth. Cen'pedes ready to march. Soon they attack us. Then is all over."

On the other lizard, little Al Birchall tried to peer through the bright white fog of Venus. It was like attempting to gaze through a bedsheet.

MacAloon lifted a pair of infra-red binoculars to his eyes. Instantly, the glasses dispelled the blinding mist.

"See anything, Mac?" Birchall asked.

Mac stared ahead without answering. Before him lay the black, motionless ocean which covered all the planet except a few hundred large islands. At the shore he saw movement, an enormous inky wave that flowed ponderously up over the land and steadily inched forward.

Countless thousands of foot-long creatures were swarming out of the water and falling into dense marching ranks. The beasts, like huge centipedes, each had dozens of swift legs. The front half was legless, though, and looked like the human part of a centaur. It wasn't only the posture that made the resemblance. They had round heads, shaped like skulls, with deadly mandibles; and clever arms and hands grew out of their shoulders.

Centaurpedes—even more than the heat, the mud and the fog, they were man's most murderous enemy on Venus.

Silently, Mac handed the binoculars to Al Birchall.

"Bossmac," the fishman pleaded, "we go 'way, not fight cen'pedes? They kill and eat us; nothing we can do."

Mac watched Al lower the glasses from his eyes. He did it very slowly at first, then grinned when he caught Mac's gaze, and flipped the binoculars across.

"They sure look dangerous," he said.

"They are," Mac answered quietly. "They can strip the flesh off our bones in three minutes flat."

Below them, between the tall bulk of the two mounts, the fishman's long, flat head turned from Mac's face to Al's.

"Bossal, tell bossmac we not able fight cen'pedes," he begged sibilantly. "They come—" The thin, scaled hands waved excitedly, "like biggest army you ever see, make war on mine. You kill and kill, more come. Please, we go to man city!"

MacAloon jerked his lizard's reins around in the direction of the mine. Al's mount came alongside. The fishman groaned, then began trotting before them on swift webbed feet. They splashed over the eternal mud, through the ever-present white fog.

Should they give up the fight against the shrewd, heartbreakingly persistent vermin? If they did, they would have to abandon the mine which had become their lifework. They would have to blow up the place before retreating.

For all life on Venus was amphibious, but centaurpedes were deliberately trying to quit the water, knowing their semi-civilization could reach its mechanistic goal only on land.

Unable to prop the porous native rock with the brittle, primitive plastics they used instead of metals, they were striving to take over an iron mine that had already been started by human engineers. Then, with the metal they could produce, they would make tools and raise cities ... and manufacture weapons with which to push men clear off the planet.

Their forays had forced a number of mines out of existence. Two years ago, before Al Birchall became the fourth partner here, an undersea colony of 'pedes swarmed down on this place. Surrounded on all sides, the men had put up a long, bitter fight. If Adonis City, half around the globe, hadn't finally sent a rocket ship, they would have been lost.

In the rocket, Mac had tried flame-strafing with the bow jets, swooping back and forth across the black mass of besiegers. But the wily animals merely dug deep in the mud and waited till he passed overhead, then continued the attack. Since he couldn't be everywhere at once, part of the army was always surging forward. At best, the strafing only slowed down the assault.

But then Limpy Austin, up in the lookout tower, sighted foraging parties in the rear, dragging up food supplies in the form of gigantic dead meat-eaters. Mac had rocketed over the rear of the army, burning the food into useless charred fragments. Starving, the attackers were at last forced to retreat to their ocean city, but only until they could figure out a new strategy.

Mac said, "We'll stick."

Otherwise, he knew, he'd have to go back to ferrying fruit boats between South America and Antarctica. Birchall would revert to his old confidence games all over the System. Swede Steffansen would have to manipulate a freight crane on Mercury again. And Limpy Austin—well, there wasn't much a semi-cripple could do, outside of being lookout and radio operator for his friends.

The two riders approached the mine enclosure which struggled into visibility through the smothering haze. The fishman, fleeter than the lumbering saddle-lizards, had already reached the high wire fence. He gestured wildly at the guard nearest him, an alert armed Venusian who stood on a stilt-platform that overlooked the fence to the mud flats beyond.

The guard pressed a button that opened a gate in the wire barricade. The mounted men pounded through, and over the wide muddy stretch to the concrete wall.

Deeply embedded in the ooze, with the rock bed for a foundation, the wall paralleled the outer fence and closed in the entire mining grounds. Its polished outer face was deeply indented, like a sharply curved concave lens. No joints showed in the smooth surface.

But Limpy Austin, up in the glass-walled lookout room atop the stilt blockade house, saw them. He opened a tightly fitting door in the concrete rampart. They rode through into the compound, dismounted near the closed-cabin freight tractor that stood beside the smelter.

"The 'pedes are coming, aren't they?" asked a slow, heavy voice behind them. Swede Steffansen came around the lizards. He was a big, placid man, but his sky-blue eyes—blue as the heaven of Earth, not this white hell—were troubled now. He said: "I could tell by the way the pack animals are acting. They're touchy."

"They caught the scent," Mac answered. "The attack's due in about two hours. Let all the animals out. We don't want them stampeding during the battle."

Swede nodded, slogged off toward the corral.

"Tell the fishmen we're in for a fight with 'pedes," Mac ordered Birchall. "Weed out the weak sisters. They'd only get in our way, anyhow."

Stepping high to avoid splashing, Al bounded off in the direction of the tipple at the mine entry. MacAloon went into the blockade house and climbed to the lookout room.

Limpy Austin was standing at the infra-red glass wall. His left arm and leg were shriveled, and one side of his face was twisted up in a sardonic leer. Mercurian Paralysis, that strange disease which immobilizes either half of a person depending on whether it is contracted at the Day or Night Side, had made a hopeless cripple of him.

He turned around when Mac came in. "Well?" he asked.

"They're coming, all right," Mac grunted. He leaned over the control panel, pushed the button that clanged the cease-work alarm down in the mine. Then he threw the lever that halted the ore cars to bring the men to the surface.

"How do things look?" Limpy pursued.

Mac shrugged. "We ought to have a better chance than before. There are four of us this time."

Limpy shuffled to the radio. With his slender, sensitive right hand, he twisted the dials.

"Adonis City," he said harshly into the microphone. "Limpy Austin calling Adonis City...."

There was a squeal of static. "Adonis City," replied a harried voice. "Come in, Austin, but make it short!"

"What's up?"

"'Pede attack on every damned mine. How about you? Aren't they—"

"Yeah," Limpy cut in. "That's why I'm calling. Send over a ship. Ours is wrecked."

The weary voice cursed. "I can't, Austin. We figured you had a boat, so we shipped them all to the other mines."

"Okay," Limpy shrugged. "Then we'll have to do without."

"Why don't you guys blow up the place and leave?"

"Maybe we'll have to. I don't know. When you get a chance—"

"Yeah," the man replied hastily. "The first ship that comes in, you guys get. So long, and good luck!"

Limpy switched off and glanced inquiringly at Mac, his paralyzed grin a slash of seemingly pure evil.

"Looks bad, Mac."

"Maybe," MacAloon said curtly. "If we can hold out till they give us a boat, we'll come through all right."

Nevertheless, he frowned, worried by the simultaneous attacks. There was something ominous behind them—and he didn't know what.

Limpy was sullen; the more the right side of his face drew down in anger, the more sardonically leered the frozen left side. Swede's placid features showed no emotion, but his clenched fists did. Mac alone tried to appear cheerful, though his mind was furiously analyzing their grave situation. While Birchall said nothing, peering absently into space.

Silently, the men pulled on steel-soled shoes, lead-fiber gloves and infra-red goggles. On their backs they strapped compact battery-radios with short antennae, a fixed microphone at the chest. The loudspeaker atop each small set, at neck level, could be heard in anything short of a vacuum or explosion. Then the defenders armed themselves with flame-throwers and machine guns that shot steel-piercing bomb bullets.

Straightening, Mac asked: "How many fishmen are staying?"

"Twenty-one," snarled Birchall.

Mac grinned wryly. "Cheer up, Al. That's better than I figured on." He turned. "Limpy, stay up at lookout. Warn me when the 'pedes are getting close. Swede, you and Al set up ammunition dumps in the compound. Then make sure the explosives and contacts will work fast if we have to blow up the place in a hurry."

While the others dispersed, Mac gathered a squad of fishmen, armed with flame-throwers and led them outside the high fence. Methodically, they burned down all vegetation for a distance of several hundred yards, to prevent the centaurpedes from creeping up close under cover.

When Mac and his detachment were returning, Limpy opened a sluice from the central control tower. Oil poured into the shallow water-filled moat that ringed the wire barrier. A thick, greasy film spread over the water.

Meanwhile, the rest of the fishmen had been deployed around the inside of the fence. They stood nervously holding their flame-throwers, their membrane-covered eyes bulging anxiously. Up on the stilt towers, the best native marksmen pressed their quivering scaled shoulders against the stocks of mounted machine-guns.

Mac felt a pang of gratitude. He knew what their decision to stay had meant. All life on Venus dreaded the centaurpede with a blind, wild terror.

"Hey!" Limpy's voice grated through the radio. "Come up to the lookout room!"

MacAloon rushed through the mud and climbed to the glass-walled chamber. He glanced questioningly at Limpy. The lookout man wordlessly handed him a pair of binoculars and pointed to the coast.

Swede and Al burst in, as usual, asked no questions. But Birchall was babbling at a terrific rate.

"Shut up!" Limpy said tensely.

Mac stared at the ocean. His jaw muscles suddenly bunched into hard knots. At wide intervals, six black waves were lapping over the shore and rolling down on the mine like a flood—a deluge with gigantic mandibles and fiendish cunning, a torrent miles long and spread far over the muddy plain.

"That's never happened before," Limpy whispered. "It was always one colony to a mine."

Swede and Al took turns at the binoculars. No change came over Swede's face. Birchall's, though, contracted in horror.

"They got together!" he yapped. "We're done for, Mac! We can't fight six colonies all at once, and without a boat!"

Scowling, Mac jammed his hands into his pockets. "They're using holding attacks on the other mines to tie up help from Adonis City. Meanwhile, they're concentrating their main force here."

"Smart little devils," rumbled Swede.

"We ought to quit!" Al chattered. "We can't lick them!"

His face whiter and more contorted than ever, Limpy said: "Why don't you guys beat it?"

Mac's head jerked up sharply. Swede looked at Limpy in mild surprise. Al Birchall's chin dropped.

"What do you mean—us guys?" Al demanded. "What about you?"

Both sides of Limpy's face grinned sardonically. "No boat, all the animals set free—you'll have to run for it. And me? Well, I'm not much good at running. But you three can escape, if I'm not along to hold you back."

"I'm a heel," snarled Birchall. "Forget what I said."

"Sure, Limpy," Swede added with clumsy joviality. "This little ape is always talking before he thinks. We're sticking—all of us."

"Cut it out!" snapped Limpy. "Somebody has to stay here to throw the dynamite switch. I don't need any help."

"Nobody's throwing any switch," Mac declared. "This is our mine, and no damned vermin are taking it over!"

"But you'll never beat them," pleaded Limpy. "And even if you did, they'd only keep coming back until they got the place. You can't wipe them out once and for all."

"Someday, somebody will," Mac said. "In the meantime, we can fight like hell. 'Pedes haven't any more intelligence than a bee, but even they get tired of being slaughtered."

"A bee?" Al asked. "I thought 'pedes were smart devils."

"Not individually, according to Graves, the old-time biologist."

"Then how can they plan and act all together?"

"They have some way of coordinating, Graves claimed. How does a beehive act as a unit? We don't know, but it does just the same."

"Can't I talk you fellows into leaving?" begged Limpy.

"No!" Al stated flatly.

Limpy shrugged. Shuffling over to the window, he pointed down at the closed-cabin tractor beside the smelter.

"Then how about letting me use that as a tank?" he asked. "I'm not much good here, anyhow. The 'pedes wouldn't be able to get at me, inside the cabin, and I could crush and burn them down till they quit."

"That was tried once at a mine," said Mac. "The 'pedes dug tank traps. The driver killed himself after being stuck in one for a week. It didn't matter; he'd have died soon enough. But even when he skipped the traps, the 'pedes dodged the treads. They don't just stand around and wait to be crushed."

The right side of Limpy's face drew down in disappointment. "You guys are suckers to stick around. I'm just a rubber cog."

"Rubber cog, huh?" Al yelped. "How do you think we're going to fight without a lookout man?"

"Don't talk like a sap, Limpy," added Mac with gruff gentleness. "We need you a lot more than you need us."

A slow, sad smile spread over Limpy's twisted features.

"Okay, if that's how you feel about it."

"That's how we feel about it," Swede answered.

They went down to their stations within the enclosure. In deadly silence, the camp waited for the first blow.

It came when the tension was almost unbearable. Through his infra-red goggles, MacAloon could see a vast, dark smear, advancing inexorably, like the ominous march of a black glacier. Before the ordered ranks came the expected stampede of animals.

As if they had studied the break-through tactics of the extinct Nazis, the 'pedes were driving huge beasts ahead of them, living tanks that were meant to smash down the mine's fortifications. Enormous meat-eaters were thundering along on vast legs, crushing smaller carnivores in their frenzied flight. Fleet, timid vegetarians raced beside their killers, but neither thought of anything except the hideously lethal creatures close behind them.

When the animals were close to the fence, Mac snapped an order into his microphone. Instantly, flame-throwers spat at the pool of oil surrounding the mine. A fierce blaze sprang up.

The demented rabble scattered right and left—all but the meat-eaters, the biggest beasts on Venus. Too stupid to fear fire, they were the greatest danger. In idiot terror, they crashed toward the fence.

Somehow, the fishmen stood their ground. Mac knew how they felt. It was a sensation of unnerving horror to watch a gigantic animal plunging toward you, to stare at the enormous fangs in the slavering yard-wide mouth, to feel the ground trembling beneath their tremendous feet....

MacAloon opened fire. From every side of the camp, he heard answering blasts. The pounding of the machine-guns made a furious clatter. Bullets exploded savagely in the great bodies. Then horrible bellows of agony drowned every other sound.

For minutes after a man managed to pump an endless burst of slugs into a meat-eater, and saw the flesh erupt in bloody blobs, he couldn't help shaking, though he knew the monster was already dead on its feet. Then the vast beast collapsed into the mud with a deafening splash, and he wondered if he could ever forget the terrifying sight.

When the thick, oily smoke thinned out, the smaller animals had fled into the fog. Mac sent out a squadron of fishmen, who destroyed the dying meat-eaters. If the bodies had been allowed to remain, the 'pedes would have used them as a food supply.

The fishmen came back inside, and all the fog-wrapped world was silent. On noiseless feet, the oncoming army moved with impossible precision toward the camp.

Twenty-five defenders against uncounted millions, with only a web of wiring and a concrete wall between them and the jaws of doom. And even if they won, victory would be no more than a truce....

The six armies of centaurpedes met and fused. Narrower and narrower grew the gap between the mine and the unending wave of repulsive vermin. Then, when they were almost at the fence, the main army suddenly slowed down, and the two wings broke into double-swift march, advancing on both sides of the barrier.

"Turn on the juice!" Mac snapped into his microphone.

Abruptly, the fence began shooting off big blue sparks in the wet air. The main body of centaurpedes halted a few yards away and remained impassive. Inside, the fishmen stood frozen, staring in terror at the long, multi-legged animals, the round, intelligent-looking heads, the huge mandibles, and the upright shoulders with pairs of clever hands and arms.

Behind the camp, the encircling wings met and joined. More advanced until the surrounding army was uniform in depth. Then, with a single movement, the black cataract flooded straight at the wire fence.

"Hold your fire!" Mac yelled at his fishmen.

Around the compound, he heard Swede and Al shouting the same order. But it was too much to expect of fear-tightened native nerves. Spasmodic bursts of fire spurted out. Undaunted, the horde pressed on against the fence.

Crackling and flashing, the electrified wire suddenly flung out great streamers of sparks. The moist chitinous bodies shriveled into ashes. A stink of burned flesh polluted the heavy fog.

Apparently at an inaudible signal, the entire mass of 'pedes fell back out of danger. MacAloon was awed. He knew that the rear of a human army, unable to see what was happening up front, would keep pushing forward. But a secret knowledge, impossible to men, made the centaurpedes act as a single entity.

Looking along the fence, Mac could see detachments of 'pede scouts, moving warily toward the sparking barrier. While the army watched, the reconnoiterers experimentally touched the wire. A flash and they were destroyed, but not before serving their purpose. They had given the army a chance to analyze the fence's properties.

Again the entire force moved forward, this time with more caution than before. MacAloon looked on anxiously, knowing they were aware of the danger.

"Mac!" cried Al's voice. "What're they going to do?"

"They're too smart to keep electrocuting themselves," said MacAloon tersely. "They must have a plan."

"But what is it?"

"I don't know," Mac admitted.

The first ten lines halted within a foot of the flashing barricade. The next nine marched forward and mounted the backs of the first lines. Then each succeeding rank climbed those in front.

"A pyramid!" Al yapped.

The fishmen gaped up at Mac, then back at the 'pedes. They were close to cracking.

"Wait!" Mac ordered. "Wait till boss-limpy says they're almost to the top of the fence. Then fire low. Don't keep firing after the pyramid falls!"

The sporadic firing ceased. Immense gaps had appeared in the pyramid, but the fence had heated red. The drain on the generators would be enormous, and this MacAloon had feared more than the few invaders that might drop across.

Swiftly, the pyramid grew until it was as high as the fence. Then, up in the lookout room, Limpy barked a signal.

Flame leaped out at the lowest line of 'pedes, slashed back and forth. All in an instant, the pyramid collapsed. The centaurpedes retreated, leaving a ring of charred bodies around the fence. But the survivors were as numberless as ever.

In the sudden silence, agonized shrieks rang out across the compound.

"What's wrong, Limpy?" demanded MacAloon.

"It's Al, but I can't see what happened!"

"Stay where you are, Swede!" Mac ordered. "Keep the fishmen fighting!"

He raced to Birchall's station, saw that Al's flame-thrower had jammed. Hundreds of centaurpedes had hurled themselves over the fence and surrounded two natives. Others had brought up a tree trunk and hammered a big hole in the wire. Through the gap, a full regiment was pouring into the enclosure.

"Take care of the ones inside!" Al shrieked. "I'll stop them!"

"Don't be a fool!" shouted Mac. "Fall back and get another flame-thrower!"

Unheeding, Al smashed a path to the fence with the butt of his weapon. 'Pedes were already climbing up his body and wasting no time. He bit his lip and charged on. The trickle of blood running down his chin was the smallest one flowing from his torn flesh. In a last desperate lunge, he grabbed the ends of the broken fence.

"Al!" Mac cried out.

He was too late. A sheet of blue flame had sprung up. There was a piercing scream of pain beyond endurance. Then Birchall hung limply, caught, as he had intended, by the jagged ends of wire. His mangled, lifeless body, through which the current flowed, had closed the gap.

A sudden film spoiled Mac's vision. Savagely, he blinked it away. With vicious fury, he burned down the swiftly crawling centaurpedes around him. The two fishmen, no longer surrounded, shuddered free of their fright and began to help. Under the fierce heat, all the animals in the enclosure curled and died.

Murderously calm, Mac fired a steady blast through the fence at the pyramid outside. Sizzling and frying, the formation fell to the ground.

In spite of that, the 'pedes had won this battle. They had unleashed a new weapon while the defenders had turned to watch the struggle. A rain of vermin seemed to come from the sky. For, thrust deep into the mud outside the fence, were whip-like catapults. Ten animals were drawing back each slingshot, flinging a 'pede into the enclosure!

Dismayed, MacAloon watched them hurtle over the wire in unbelievable numbers. Shooting wildly at them, yet fixed to the ground they were defending, the fishmen were desperately near panic.

"Stop firing!" Mac shouted.

His order was ignored. He cursed and pulled half of the natives away, giving their flame-throwers to the remaining guards. The first half he sent inside the compound with snapped instructions. The others he placed just before the concrete rampart. Armed with two weapons instead of one, each fishmen had double firing power.

"Let them reform their ranks inside the camp," Mac ordered. "Then let them have it!"

Limpy communicated the command to Swede on the other side of the compound. The haphazard blasts stopped. Undisturbed now, the centaurpedes well into military formation, as Mac had expected. When their lines were twenty deep, they advanced, a black, tight unit with champing mandibles.

"Now!" MacAloon roared.

A withering wall of flame lashed out, burning down the invaders by the hundreds. But reinforcements kept flying over the blue-flashing fence. And under cover of the air invasion, the pyramids were being built again! The fishmen, backed up against the curved concrete barricade, were unable to reach this new threat with a stream of fire.

Obeying his previous instructions, a squad of fishmen came staggering through the doors in the wall. They dragged oxygen and hydrogen tanks that were connected in pairs by flexible, insulated hoses with triggered nozzles.

"Forward!" Mac commanded.

Limpy passed the word around the besieged mine, and fishmen advanced with blazing flame-throwers. Behind them, the reserves hauled up the tanks. Slowly, stubbornly, the tide of centaurpedes was driven back into the fence. An ear-splitting crackle, and they were gone, a smoking pile of cinders.

Even after the camp was clear, Mac did not rest. He drove the reserves to the fence and kept them firing at the enemy beyond.

"Not the 'pedes!" he shouted. They looked up, bewildered, wondering why ammunition should be used, if not to burn down the foe. "Melt the catapults!" he ordered.

The natives understood at last that the hand-weapons were too feeble to reduce the crude plastic slingshots, but that the tank flame-throwers were not. They blasted out at the catapults.

But the centaurpedes were damnably shrewd. In half the time it had taken the fishmen to comprehend, the vermin had begun pulling up their slingshots and retreating out of range.

Harrying his forces to get the catapults, Mac glanced aside and swore viciously. In the gaps between his widely spaced crew, more pyramids were forming.

"Forget the slingshots!" he yelled. "They can wait till later!"

The revised order didn't make sense to the fishmen. They couldn't see that, while their attention was diverted, the main army could pour over the fence on a secure pyramid. They blasted away at the slingshots and ignored the wall of 'pedes.

The deadly animals saw their chance and acted. With quick cunning, they sent over a torrent of invaders. Chattering in fear, the fishmen switched their attack to the pyramids, but they were too late. They were being driven back by the vermin inside the fence, and more and more were coming over.

"I can't hold them, Mac," came Swede's unalarmed voice.

"I can't either," Mac said tensely. "Get the fishmen and fuel tanks into the compound."

Shrill screams erupted from the natives. Faced by alert, precise ranks marching toward them, they threw down their weapons and rushed for the concrete wall.

Mac ran forward, cursing. He grabbed an oxy tank and pulled it to safety. Most of the thrower fuel was safe in the camp, but the tanks outside would be badly needed if the attack continued in force. But regiments of 'pedes had by-passed the ammunition and posted guards to prevent their being rescued.

Hard-faced, Mac ordered a fishmen to go out into the enclosure with him. While Mac kept back the horde with a hail of fire, the shivering native pulled a tank into the compound. Mac increased the size of the raiding parties. Again and again they sallied out, until the bulk of the abandoned fuel was saved.

Sweating, Mac signaled to Limpy in the blockade house. The hermetic doors in the wall slid shut. The natives stood on the ledge on the inner side of the rampart, watching with horror-filled eyes as the fiendish beasts tried to scale the concave surface.

Mac called Swede by radio, then trudged through the mud to the blockade house. The three men met in the lookout room.

Seeing Swede, Mac realized for the first time how dirty, wet and exhausted he was himself. They were both blackened with mud and flame blasts, their clothing grimy and sopping.

Limpy's good eye was harrowed, the frozen side of his face contorted in an evil grin.

"Poor Al," muttered Swede. He sank down ponderously on a chair. "He was a game little fellow. I'll miss him."

Without replying, Limpy turned around. He stared sightlessly through the infra-red windows at the white fog and the eternal mud, the seething mass of centaurpedes and the shaking, gabbling fishmen. All around the mine, seeming to reach every horizon, stretched the completely encircling army of vermin. But that was not what Limpy was seeing.

Mac came over to the window. "I saw Al die, too," he said in a harshly gentle voice. "If I have to kick off that way, I hope I'll be as brave as he was."

"Maybe you'll get your chance sooner than you think," Limpy snarled. "Six armies against us, one dead, our boat no good, the fence useless, the fishmen demoralized—" He whirled. "What are we waiting for? Why don't we blow up the place and quit?"

"Because we still have a chance," Mac answered. "They've taken our first line of defense, but we still have the second."

"The wall?" Swede grunted. "Think that'll stop them long?"

"Long enough," promised Mac. "It's thirty times as high as they are, and three feet out of plumb-line with the bottom. Before they figure out how to get across, maybe Adonis City'll be able to send us a rocket. Get them on the radio, anyhow, Limpy. We're carrying the whole weight of the attack. They've got to give us a ship."

Limpy shuffled to the panel. He set the dials, then spoke mechanically into the microphone: "Adonis City. Limpy Austin calling Adonis City...." Several minutes went by. He looked up. "They don't answer."

"Keep trying," Mac said. "Everybody must be calling them from all the other mines."

"That's what I mean," Swede put in earnestly. "We fight; the other mines fight. Sometimes we win; sometimes the 'pedes do. Whatever happens, it's never finished. We spoil their old tricks, so they figure out new ones. They're devils, Mac. We can never lick them for good."

"Someday, somebody will," Mac said stubbornly.

He gripped the sill and stared out through the infra-red glass. In the outer compound was a black fester of centaurpedes, crawling like gigantic lice before the concrete barricade.

"Nothing can stop them," Swede said beside him. "They'll find a way of getting over. They always do. And then—"

Mac's skin began to creep. To be eaten, the flesh stripped off your bones while you're alive and screaming.... The fence had halted them, and they'd built pyramids. When flame-throwers cut down the pyramids, they used catapults. Now the wall was holding them back, but they'd work out some method of hurtling over.

Then those armored bodies would push back the defenders until they could retreat no farther. Before those steel-hard mandibles, one man after another would go down, a living skeleton, covered with black, crawling vermin....

Mac shuddered. "As long as that wall holds them," he said, "it isn't hopeless. But the sooner the boat gets here, the better off we'll be. Are you trying Adonis City, Limpy?"

"All over the dial!" Limpy groaned. "They don't answer!"

Swede shook his head. "The fishmen know what the odds are. Look at that."

Mac saw three natives fling up their arms, claw over the wall and throw themselves into the 'pedes' jaws. They fought to their feet and raced toward the fence, but their fleetness didn't save them. Long before they reached the wire, they were black and shapeless, covered from head to foot with clinging, rending animals.

"The fence," Swede explained quietly. "That's why they went crazy."

Far to the right, a corps of centaurpede engineers had hauled up the huge tree trunk. Using it as a battering ram again, they smashed down a section of the barrier. Now they were rushing in, tearing the chargeless fence to pieces. As the two men watched tensely, another section collapsed with a splash into the mud. Instantly, the 'pedes began moving it toward the concrete wall.

"I knew they'd find a way," said Swede. "They're going to use the fence segments as ladders." He turned away.

Mac, continuing to stare down, suddenly stiffened. The 'pedes were acting queerly, moving around sluggishly, as if they had lost interest in their task! He frowned and faced his companions.

"That's funny," he muttered. "They're stopping—they seem confused."

Limpy shrugged and went on twirling the dials. Swede glanced out, then looked at Mac with upraised eyebrows.

"They look the same to me," he said slowly. "You seeing things, Mac?"

Startled, MacAloon shot his gaze back to the scene below. Swede was right! The 'pedes had resumed their work! Mac stood still for a moment, his mind racing swiftly, trying to grasp the significance of that momentary halt. Then he whirled, facing Limpy.

"What were you doing just a moment ago?"

Limpy raised his head from the dials. "Trying all the wave lengths. Adonis City isn't on its usual—"

"I thought so!" Mac yelled triumphantly. "Get back to the length you had before!"

"But there wasn't any answer."

"They're halfway to the wall," Swede muttered abstractedly.

"Get that wave length again!" Mac snapped.

Limpy's right shoulder shrugged. He twisted the dial gently while MacAloon turned back to the window and stared out tensely.

"Hold it!" he suddenly ordered. "Don't touch those dials!"

Swede and Limpy looked at him puzzledly. He pointed down at the swarming enclosure. Limpy shuffled over to him, followed the direction of his finger.

"They've dropped the fence," whispered the lookout. "They don't seem to know what they're doing."

"Yah," Swede said in an awed voice.

Below, the centaurpedes were moving about aimlessly, as if they had forgotten their orders. They had completely lost their terrible machine-like precision!

"I don't get it," Swede complained in bewilderment. "What's wrong with them?"

Mac's grin was hard and tight. "They're directed by a central brain, a sort of queen 'pede which coordinates their actions by ultra-short-wave commands, the way a queen bee directs a beehive. That's the secret of their synchronization!"

"And I was working the ultra-short—" Limpy stopped, stunned.

"That's the idea," Mac nodded. "Our signals blanket theirs! They can't get orders from the main intelligence, so they don't know what to do!"

For a moment, the men were silent. Slowly, then, Swede said: "Now all we have to do is kill the brain."

"Yeah," Limpy agreed bitterly. "What a chance of getting through! Where's the queen 'pede, or the brain, or whatever it is?"

Mac squinted through a pair of binoculars. He gazed along that meandering tangle of disorganized vermin. Abruptly, he halted. A mile beyond the ravaged fence was a small patch of integrated activity, a regiment of centaurpedes that still functioned in unison.

"There's the truth," he muttered. "Or more likely, there are six of them, one from each undersea colony. They probably formed a council of war to attack us. That's why we almost lost."

"Almost?" Swede echoed. "But we can't fight them now!"

Mac shook his head. "We won't lose," he said grimly. "I'm going to kill the council of war."

"You're crazy!" Limpy cried. "You'd have to run through a mile of mud and 'pedes. Brain or no brain to direct them, they'll pull you down instinctively. Mac, you won't have a chance!"

MacAloon looked out at the wandering army. "I think I will," he said. He went to the door. "They won't attack together. Open the wall, Limpy. Don't mind if a few 'pedes get through. You can take care of them. Just keep that ultra-short-wave blanket clamped down over their minds. So long."

He ran down the metal steps and across the mud toward the smelter. Tearing open the door of the closed-cabin tractor, he jumped inside and slammed the port shut. He started the motor, drove past the blockade house. Swede and Limpy were at the window. Mac waved.

A door in the wall swung wide for him. He tooled through, the door closed and he was among the centaurpedes. Infinitely disgusting things, a few individuals attacked the tractor in blind rage, clamping their mandibles on the steel parts and clinging senselessly. Others gaped up in blank wonder as the machine bore down on them. He heard them crack and squish beneath the threads.

He drove straight at the fence. It went down and he was out of the enclosure, entirely surrounded by vermin. On all sides, farther than he could see, were purposeless animals, no longer in orderly ranks, obeying a single dictate. How long would they remain severed from the controlling brains?

Desperately, Mac fixed in his mind the position of the place where he had seen unified activity. He headed directly for the war council of intelligent centaurpedes.

The treads of his tractors made sucking, splashing sounds through the mud. 'Pedes, not bright enough by themselves to get out of the way of danger, died by the thousands under the grinding chains.

He was drawing closer, into the thickest cluster of all. The vermin here were also wandering around, but they seemed to be trying to make up their minds. Mac knew the blanketing wave was weaker here, that the council of queens 'pedes was struggling to get its nearer minions under control again. Before that happened, they had to be destroyed.

But where were they? Two hundred yards away was a great battle square of centaurpedes, setting themselves with idiot bravery to stop his invincible machine. Mandibles opened wide, they crouched back, ready to spring and rend the indestructible steel.

Were the 'pede dictators in the center of that battalion? Theoretically, they should be, but Mac knew better than to expect the obvious. Were they brain-like, slug-like, or did they hide their vast significance behind protective disguises of mediocrity, pretending to be nothing but ordinary centaurpedes?

The tractor lumbered on across the mud, smashed into that wall of nauseating bodies. The cracking and squashing made his stomach heave, yet he kept grinding ahead.

"Damn your murdering hearts, where are you?" he bit out.

He crashed through the battalion, started to turn back for another charge. Instead, he clamped his teeth together and continued savagely. Far before him, he had seen several 'pedes, identical with the rest, racing in different directions toward the ocean. They had set up a rear guard to cover their retreat.

He wrenched the wheel aside. Crack!

"One!" he gloated.

Another was scampering furiously twenty feet ahead. He drove down on it, exulted when he heard the treads crush the hard chitinous shell.

"Two!"

"Three!"

The revolting beasts were fleet, but the tractor was swifter. One after another, he ran them down, his lips twisting in a fierce grin each time he heard one squash beneath his treads.

At last, two miles from camp, he stopped. He had destroyed the last 'pede trying to escape to the ocean. But had he killed the brains that had directed this gigantic assault on the mine?

He pivoted and started back to the compound. The 'pedes were still ambling around, following their single purposes. He could never have got through if the ultra-short wave hadn't actually blanketed the brains' commands. But were the animals merely disorganized only as long as the broadcast continued, or had their rulers really been killed?

Mac reached the mine. Limpy opened a gate in the concrete wall, and he drove through. A moment later, he was in the lookout wall, standing beside his two partners, gazing out the window.

"Did you get them?" Limpy asked breathlessly.

Mac leaned forward and watched with intent eyes. Slowly, like brainless creatures gradually coming to a decision, the endless mob of centaurpedes began moving away. They didn't march, as they had advanced to the attack. They wandered off in the general direction of the sea from which they had sprung.

"I got them," Mac said. He straightened and turned around wearily. "Get in touch with Adonis City, Limpy. Give them the wave length that blankets the queen 'pedes' instructions. Tell them to relay the information to mines that are under siege."

"We've won?" asked Swede incredulously.

"Yes," Mac replied. "And this time it's for good. We'll be able to beat off every attack from now on. Only, I don't think they'll go on fighting much longer. They'll have to quit."

Swede sat down ponderously. "I'm glad, Mac. Not for us; for Al. He didn't die uselessly."

"No," Mac said. "He didn't."

Fumbling with the radio dials, Limpy grinned. None but his close friends could know that grief made his grin wider and more evil-looking than ever.