"Why, you clumsy--" Brett roared, raising his gun menacingly.

Astro stepped in front of Tom. "I'll get it," he cried. "Don't shoot!"

"Go on then," snarled Brett. "Go down with him, Miles. I'll stay here with Corbett."

"You go down with him," sneered Miles. "I've been up and down that ladder fifty times while you sat up here doing nothing."

"Is that so?" cried Brett angrily, turning to face the black-clad s.p.a.ceman. This gave Tom the opportunity he was waiting for. He pulled the small charge of explosives from his tunic and held it in front of him.

"All right, you two!" he shouted. "Drop those paralo-ray guns. This is the b.o.o.by trap you planted in the tunnel. You fire those ray guns and we all go up together."

Brett jumped back. Miles took a half step forward and stopped. "You haven't got the nerve," he sneered.

"Shoot and you'll find out," said Tom. "Go ahead! Shoot, if you've got the guts. Get down the ladder, Astro," he said. "They won't fire as long as I've got this in my hand."

Brett had begun to shake with fear but Miles brought his ray gun up slowly. He aimed it at Astro who was starting down the ladder, his head and shoulders still showing in the open air-lock portal. Tom saw what Miles was going to do. "Jump, Astro!" he shouted.

Astro jumped at the exact instant Miles fired. "Rush him," cried Miles.

Brett made a headlong dash for Tom, but the cadet side-stepped at the last moment and Brett fell headlong out of the ship, wailing in sudden terror as he fell to the ground.

Miles turned to Tom. He ripped off his mask and with his free hand closed the air-lock portal.

"You fooled Brett, but you didn't fool me, Corbett." He laughed. "It takes a direct electric charge to set that stuff off. You just helped me get rid of a very obnoxious partner." He leveled his paralo-ray gun.

"I hate to do this," he said, "but it's you or me."

He fired. Tom was again frozen into that immobile state more dead than alive. Miles laughed and hurried to the control deck.

Astro got up on his knees slowly. Though the fall had been a hard one, he had rolled quickly with the first impact, thus preventing any injuries. He shook his head, regained his sense of direction, and then rose to his feet, starting back to the ship in hope of helping Tom. He tripped over something and fell to the ground. Groping around in the thickening ammonia gas he felt the still form of a body. For a moment, thinking it was Tom, his heart nearly stopped, and then he breathed a silent prayer of thankfulness when he recognized Charley Brett. He felt the man's heart. There was a faint beat.

Astro opened the valve on Brett's oxygen mask wide and waited until the man was breathing normally. Then he began feeling his way back to the ladder. Suddenly he heard a sound that made his blood run cold. It was the unmistakable whine of the cooling pumps building for blast-off. And he was directly underneath the exhaust tubes.

He scrambled away, heading back to the spot where Brett lay. The whining of the pumps built to an agonizing scream. There were scant seconds left to save himself. He could not wait to find Brett. He began running wildly away from the ship, stumbling, failing, rising to his feet again to plunge on, away from the deadly white-hot exhaust blast of the _s.p.a.ce Knight_.

[Ill.u.s.tration]

There was a terrific explosion, and then Astro was lifted off his feet and hurled through the mist, head over heels. He screamed and then blacked out.

"We found him about a thousand yards away from the warehouse, Commander," said the guardsman. "He looks pretty beat and his clothes are burned a little. I think he must have been caught in the blast of that ship we heard take off."

Walters looked down at Astro's big frame, sprawled on the ground, and then at the medical corpsman who was giving him a quick examination. The corpsman straightened up and turned to Walters and Captain Strong.

"He'll be all right as soon as he wakes up."

"Shock?" asked Strong.

"Yes. And complete fatigue. Look at his hands and knees. He's been doing some pretty rough work." The corpsman indicated the big cadet's hands, skinned and swollen from his labor in the mines.

"Wake him up!" growled Walters.

"Wake him up!" exclaimed the corpsman. "Why, sir, I couldn't allow--"

"Wake him up. And that's an order!" insisted Walters.

"Very well, sir. But this will have to go into my report to the senior medical officer."

"And I'll commend you for insisting on proper care for your patients,"

Walters stated. "But in the meantime we've got to find out what happened. And Cadet Astro is the only one who can tell us."

The corpsman turned to his emergency kit. He took out a large hypodermic needle, filled with a clear fluid, and injected it into the big cadet's arm.

In less than a minute Astro was sitting up and telling Walters everything that had happened. When he told of the pipe that was sucking off the oxygen from the main pumps, Walters dispatched an emergency crew to the mine immediately to plug the leak. Then, when Astro revealed the secret of the mine, the presence of the uranium pitchblende, Walters shook his head slowly.

"Amazing!" he exclaimed. "Greed can ruin a man. He could have declared such a discovery and still had more money than he could have spent in a lifetime."

Walters spun around. "Steve, I want the _Polaris_ ready to blast off within an hour. We're going after one of the dirtiest s.p.a.ce rats that ever hit the deep!"

[Ill.u.s.tration]

CHAPTER 18

Roger peered around the edge of the baffling shields. The power deck was empty. He edged out and stood upright, eyes moving constantly for signs of Miles.

No longer needing the c.u.mbersome s.p.a.ce suit, he stripped it off and walked across the deck to the ladder. He stopped to listen again but there was only the sound of the rockets under emergency s.p.a.ce drive. A quick glance at the control panel told him that the ship was hurtling through s.p.a.ce at a fantastic speed. Satisfied that Miles was nowhere near, Roger gripped the rocketman's wrench tightly and began climbing slowly and cautiously.

When he reached the next deck, he raised his head through the hatch slowly. Then, in one quick movement, he pulled himself up on the deck and ran for cover behind a small locker to his right. Above him, through the open network of frames and girders, he could see the control deck, but Miles was nowhere in sight.

Something on the opposite side of the ship caught his eye. Miles' s.p.a.ce suit hung on its rack, the heavy fish-bowllike s.p.a.ce helmet beside it in its open locker. Roger's heart skipped a beat as he noticed the holster for a paralo-ray gun nearby. But the large flap was closed and he could not see if it held a gun.

[Ill.u.s.tration: _Slowly and cautiously he began climbing_]

The young cadet moved away from the protection of the locker and started toward the s.p.a.ce suit. He moved slowly, watching the upper deck where he figured Miles would be at the control board, operating the ship.

Suddenly Miles appeared above him, walking across the open control deck with a clip board in his hand, making a standard check of the many instruments. Before Roger could find a hiding place, Miles saw the cadet. He drew his paralo-ray gun quickly, firing with the speed of a practiced hand. Roger dove toward the s.p.a.ce suit and wrenched open the holster but found it empty. Miles was behind him now, running down the ladder.

Roger spun around, darted to the ladder leading to the power deck, and just missed being hit by Miles' second shot. He jumped the ten feet to the power deck and darted behind the huge bank of atomic motors.

Miles came down the ladder slowly, gun leveled, eyes searching the deck.

He stopped with his back to the rocket motors and called, "All right, Manning, come on out. If you come out without any trouble, I won't freeze you. I'll just tie you up again."

Roger was silent, gripping the wrench tightly and praying for a chance to strike. Miles still remained in one position, protected by the motor housing.