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.

CHAPTER EIGHTEEN

Jupiter and the Jovian worlds leaped suddenly backward, turned swiftly green, then blue, and faded in an instant into violet. The Sun spun crazily through space, retreating, dimming to a tiny ruby-tinted star.

The giant generators in the Invincible hummed louder now, continually louder, a steel-throated roar that trembled through every plate, through every girder, through every bit of metal in the ship.

The ship itself was plunging spaceward, streaking like a runaway star for the depths of space beyond the Solar System. And behind it, caught tight, gripped and held, Craven's ship trailed at the end of a tractor field that bound it to the space-rocketing Invincible.

The acceleration compensator, functioning perfectly, had taken up the slack as the ship had plunged from a standing start into a speed that neared the pace of light. But it had never been built to stand such sudden, intense acceleration, and for an instant Russ and Greg seemed to be crushed by a mighty weight that struck at them. The sensation swiftly lifted as the compensator took up the load.

Greg shook his head, flinging the trickling perspiration from his eyes.

"I hope their compensator worked as well as ours," he said.

"If it didn't," declared Russ, "we're towing a shipload of dead men."

Russ glanced at the speed dial. They were almost touching the speed of light. "He hasn't cut down our speed yet."

"We threw him off his balance. His drive depends largely on the mass of some planet as a body to take up the reaction of his ship. Jupiter is the ideal body for that ... but he's leaving Jupiter behind. He has to do something soon or it'll be too late."