It was a weird revolution. There were few battles, little blood shed. There seemed to be no secret plots. There were no skulking leaders, no passwords, nothing that in former years had marked rebellion against tyranny.

It was a revolution carried out with utter boldness. Secret police were helpless, for it was not a secret revolution. The regular police and the troopers were helpless because the men they wanted to arrest were shadows that flitter here and there ... large and substantial shadows, but impossible to seize and imprison.

Every scheme that was hatched within the government circles was known almost at once to the ghostly leaders who stalked the land. Police detachments, armed with warrants for the arrests of men who had participated in some action which would stamp them as active rebels, found the suspects absent when they broke down the doors. Someone had warned them. Troops, hurried to points where riots had broken out, arrived to find peaceful scenes, but with evidence of recent battle. The rioters had been warned, had made their getaway.

When the rebels struck it was always at the most opportune time, when the government was off balance or off guard.

In the first day of the revolt, Ranthoor fell when the maddened populace, urged on by the words of a shadowy John Moore Mallory, charged the federation buildings. The government fled, leaving all records behind, to Satellite City on Ganymede.

In the first week three Martian cities fell, but Sandebar, the capital, still held out. On Venus, Radium City was taken by the rebels within twenty-four hours after the first call to revolt had rung across the worlds, but New Chicago, the seat of government, still was in the government’s hands, facing a siege.

Government propagandists spread the word that the material energy engines were not safe. Reports were broadcast that on at least two occasions the engines had blown up, killing the men who operated them.

But this propaganda failed to gain credence, for in the cities that were in the rebel hands, technicians were at work manufacturing and setting up the material engines. Demonstrations were given. The people saw them, saw what enormous power they developed.

Russ Page stared incredulously at the television screen. It seemed to be shifting back and forth. One second it held the distorted view of Satellite City on Ganymede, and the next second the view of jumbled, icy desert somewhere outside the city.

“Look here, Greg,” he said. “Something’s wrong.”

Greg Manning turned away from the calculator where he had been working and stared at the screen.

“How long has it been acting that way?” he asked.

“Just started,” said Russ.

Greg straightened and glanced down the row of television machines. Some of them were dead, their switches closed, but on the screens of many of the others was the same effect as on this machine. Their operators were working frustratedly at the controls, trying to focus the image, bring it into sharp relief.

“Can’t seem to get a thing, sir,” said one of the men. “I was working on the fueling station out on Io, and the screen just went haywire.”

“Mine seems to be all right,” said another man. “I’ve had it on Sandebar for the last couple of hours and there’s nothing wrong.”

A swift check revealed one fact. The machines, when trained on the Jovian worlds, refused to function. Anywhere else in space, however, they worked perfectly.

Russ stoked and lit his pipe, snapped off his machine and swung around in the operator’s chair.

“Somebody’s playing hell with us out around Jupiter,” he stated calmly.

“I’ve been expecting something like this,” said Greg. “I have been afraid of this ever since Craven blanketed us out of the Interplanetary building.”

“He really must have something this time,” Russ agreed. “He’s blanketing out the entire Jovian system. There’s a space field of low intensity surrounding all of Jupiter, enclosing all the moons. He keeps shifting the intensity so that, even though we can force our way through his field, the irregular variations make it impossible to line up anything. It works, in principle, just as effectively as if we couldn’t get through at all.”

Greg whistled soundlessly through suddenly bared teeth.

“That takes power,” he said, “and I’m afraid Craven has it. Power to burn.”

“The collector field?” asked Russ.

Greg nodded. “A field that sucks in radiant energy. Free energy that he just reaches out and grabs. And it doesn’t depend on the Sun alone. It probably makes use of every type of radiation in all of space.”

Russ slumped in his chair, smoking, his forehead wrinkled in thought.

“If that’s what he’s got,” he finally declared, “he’s going to be hard to crack. He can suck in any radiant vibration form, any space vibration. He can shift them around, break them down and build them up. He can discharge them, direct them. He’s got a vibration plant that’s the handiest little war machine that ever existed.”

Greg suddenly wheeled and walked to a wall cabinet. From it he took a box and, opening it, lifted out a tiny mechanism.

He chuckled deep in his throat. “The mechanical shadow. The little machine that always tells us where Craven is as long as he’s wearing his glasses.”

“He always wears them,” said Russ crisply. “He’s blind as a bat without them.”

Greg set the machine down on the table. “When we find Craven, we’ll find the contraption that’s blanketing Jupiter and its moons.”

Dials spun and needles quivered. Rapidly Russ jotted down the readings on a sheet of paper. At the calculator, he tapped keys, depressed the activator. The machine hummed and snarled and chuckled.

Russ glanced at the result imprinted on the paper roll.

“Craven is out near Jupiter,” he announced. “About 75,000 miles distant from its surface, in a plane normal to the Sun’s rays.”

“A spaceship,” suggested Greg.

Russ nodded. “That’s the only answer.”

The two men looked at one another.

“That’s something we can get hold of,” said Greg.

He walked to the ship controls and lowered himself into the pilot’s chair. A hand came out and hauled back a lever.

The Invincible moved.

From the engine rooms came the whine of the gigantic power plant as it built up and maintained the gravity concentration center suddenly created in front of the ship.

Russ, standing beside Greg at the control panel, looked out into space and marveled. They were flashing through space, their speed building up at a breath-taking rate, yet they had no real propulsion power. The discovery of the gravity concentrator had outdated such a method of driving a spaceship. Instead, they were falling, hurtling downward into the yawning maw of an artificial gravity field. And such a method made for speed, terrible speed.

Jupiter seemed to leap at them. It became a great crimson and yellow ball that filled almost half the vision plate.

The Invincible’s speed was slacking off, slower and slower, until it barely crawled in comparison to its former speed.

Slowly they circled Jupiter’s great girth, staring out of the vision port for a sight of Craven’s ship. They were nearing the position the little mechanical shadow had indicated.

“There it is,” said Russ suddenly, almost breathlessly.

Far out in space, tiny, almost like a dust mote against the great bulk of the monster planet, rode a tiny light. Slowly the Invincible crawled inward. The mote of light became a gleaming silver ship, a mighty ship one that was fully as large as the Invincible!

“That’s it all right,” said Greg. “They’re lying behind a log out here raising hell with our television apparatus. Maybe we better tickle them a little bit and see what they have.”

Rising from the control board, he went to another control panel. Russ remained standing in front of the vision plate, staring down at the ship out in space.

Behind him came a shrill howl from the power plant. The Invincible staggered slightly. A beam of deep indigo lashed across space, a finger suddenly jabbing at the other ship.

Space was suddenly colored, for thousands of miles, as the beam struck Craven’s ship and seemed to explode in a blast of dazzling indigo light. The ship reeled under the impact of the blow, reeled and weaved in space as the beam struck it and delivered to it the mighty power of the screaming engines back in the engine room.

“What happened?” Greg screamed above the roar.

Russ shrugged his shoulders. “You jarred him a little. Pushed him through space for several hundred miles. Made him know something had hit him, but it didn’t seem to do any damage.”

“That was pure cosmic I gave him! Five billion horsepower and it just staggered him!”

“He’s got a space lens that absorbs the energy,” said Russ. “The lens concentrates it and pours it into a receiving chamber, probably a huge photo-cell. Nobody yet has burned out one of those things on a closed circuit.”

Greg wrinkled his brow, perplexed. “What he must have is a special field of some sort that lowers the wave-length and the intensity. He’s getting natural cosmics all the time and taking care of them.”

“That wouldn’t be much of a trick,” Russ pointed out. “But when he takes care of cosmics backed by five billion horsepower ... that’s something else!”

Greg grinned wickedly. “I’m going to hand him a long heat radiation. If his field shortens that any, he’ll have radio beam and that will blow photo-cells all to hell.”

He stabbed viciously at the keys on the board and once again the shrill howl of the engines came from the rear of the ship. A lance of red splashed out across space and touched the other ship. Again space was lit, this time with a crimson glow.

Russ shook his head. “Nothing doing.”

Greg sat down and looked at Russ. “Funny thing about this. They just sat there and let us throw two charges at them, took everything we gave them and never tried to hand it back.”

“Maybe they haven’t anything to hand us,” Russ suggested hopefully.

“They must have. Craven wouldn’t take to space with just a purely defensive weapon. He knew we’d find him and he’d have a fight on his hands.”

Russ found his pipe was dead. Snapping his lighter, he applied flame to the blackened tobacco. Walking slowly to the wall cabinet, he lifted two other boxes out, set them on the table and took from them two other mechanical shadows. He turned them on and leaned close, watching the spinning dials, the quivering needles.

“Greg,” he whispered, “Chambers and Stutsman are there in that ship with Craven! Look, their shadows register identical with the one that spotted Craven.”

“I suspected as much,” Greg replied. “We got the whole pack cornered out here. If we can just get rid of them, the whole war would be won in one stroke.”

Russ lifted a stricken face from the row of tiny mechanisms. “This is our big chance. We may never get it again. The next hour could decide who is going to win.”

Greg rose from the chair and stood before the control board. Grimly he punched a series of keys. The engines howled again. Greg twisted a dial and the howl rose into a shrill scream.

From the Invincible another beam lashed out ... another and another. Space was speared with beam after beam hurtling from the great ship.

Swiftly the beams went through the range of radiation, through radio and short radio, infra-red, visible light, ultra-violet, X-ray, the gammas and the cosmics a terrific flood of billions of horsepower.

Craven’s ship buckled and careened under the lashing impacts of the bombardment, but it seemed unhurt!

Greg’s face was bleaker than usual as he turned from the board to look at Russ.

“We’ve used everything we have,” he said, “and he’s stopped them all. We can’t touch him.”

Russ shivered. The control room suddenly seemed chilly with a frightening kind of cold.

“He’s carrying photo-cells and several thousand tons of accumulator stacks. Not much power left in them. He could pour a billion horsepower into them for hours and still have room for more.”

Greg nodded wearily. “All we’ve been doing is feeding him.”

The engines were humming quietly now, singing the low song of power held in leash.

But then they screamed like a buzz saw biting into an iron-hard stick of white oak. Screamed in a single, frightful agony as they threw into the protecting wall that enclosed the Invincible all the power they could develop.

The air of the ship was instantaneously charged with a hazy, bluish glow, and the sharp, stinging odor of ozone filled the ship.

Outside, an enormous burst of blue-white flame splashed and spattered around the Invincible. Living lightning played in solid, snapping sheets around the vision port and ran in trickling blazing fire across the plates.

Russ cried out and backed away, holding his arm before his eyes. It was as if he had looked into a nova of energy exploding before his eyes.

In the instant the scream died and the splash of terrific fire had vanished. Only a rapidly dying glow remained.

“What was it?” asked Russ dazedly. “What happened? Ten engines every one of them capable of over five billion horsepower and every one of them screaming!”

“Craven,” said Greg grimly. “He let us have everything he had. He simply drained his accumulator stacks and threw it all into our face. But he’s done now. That was his only shot. He’ll have to build up power now and that will take a while. But we couldn’t have taken much more.”

“Stalemate,” said Russ. “We can’t hurt him, he can’t hurt us.”

“Not by a damn sight,” declared Greg. “I still have a trick or two in mind.”

He tried them. From the Invincible a fifty-billion-horsepower bolt of living light and fire sprang out as all ten engines thundered with an insane voice that racked the ship.

Fireworks exploded in space when the bolt struck Craven’s ship. Screen after screen exploded in glittering, flaming sparks, but the ship rode the lashing charge, finally halted the thrust of power. The beam glowed faintly, died out.

Perspiration streamed down Greg’s face as he bent over a calculator and constructed the formula for a magnetic field. He sent out a field of such unimaginable intensity that it would have drawn any beryl-steel within a mile of it into a hard, compact mass. Even the Invincible, a hundred miles away, lurched under the strain. But Craven’s ship, after the first wild jerk, did not move. A curious soft glow spread out from the ship, veered sharply and disappeared in the magnetic field.

Greg swore softly. “He’s cutting it down as fast as I try to build it up,” he explained, “and I can’t move it any nearer.”

From Craven’s ship lashed out another thunderbolt and once again the engines screamed in terrible unison as they poured power into the ship’s triple screen. The first screen stopped all material things. The second stopped radiations by refracting them into the fourth dimension. The third shield was akin to the anti-entropy field, which stopped all matter ... and yet the ten engines bellowed like things insane as Craven struck with flaming bolts, utilizing the power he had absorbed from the fifty billion horsepower Greg had thrown at him.

There was anger in Greg Manning’s face ... a terrible anger. His fists knotted and he shook them at the gleaming ship that lay far down near Jupiter.

“I’ve got one trick left,” he shouted, almost as if he expected Craven to hear. “Just one trick. Damn you, see if you can stop this one!”

He set up the pattern on the board and punched the activating lever. The ten engines thrummed with power. Then the howling died away.

Four times they screamed and four times they ebbed into a gentle hum.

“Get on the navigation controls!” yelled Greg. “Be ready to give the ship all you’ve got.”

Greg leaped for the control chair, grasped the acceleration lever.

“Now,” growled Greg, “look out, Craven, we’re coming at you!”

Greg, teeth gritted, slammed the acceleration over.

Suddenly all space wrenched horribly with a nauseating, terrible thud that seemed to strain at the very anchors of the Universe.