"I'll turn around and leave."

"Then start turning, Strong," snarled the giant prisoner, "because I ain't got nothing to tell you except how much I hate your guts!"

Astro moved forward slightly, but Strong held him back. "O.K., Bull. If that's the way you want it, I'll leave."

"Why don't you let the young punk try something?" challenged c.o.xine. "I ain't had any exercise in a long time."

Strong looked at the huge man and said coldly, "I wouldn't want the death of a piece of s.p.a.ce sc.u.m to show on his record."

Then, as if the s.p.a.ce and sky overhead had suddenly been torn open, there was a flash of light followed by the roar of a tremendous explosion. The ground trembled. The air seemed to moan in agony. Strong and Astro wheeled around and looked toward the tower that shimmered in the light of the late afternoon sun. To their horror, they saw the unmistakable mushrooming cloud of an atomic blast rising in the synthetic atmosphere behind it.

"By the craters of Luna--" gasped Strong.

A second flash and explosion rocked the prison asteroid and suddenly the tower disappeared. Almost immediately, a s.p.a.ceship appeared over the small planetoid and began systematically pounding the surface installations with atomic blasters.

"Captain Strong," cried Astro. "Tom and Roger--they were in the tower!"

"Come on," yelled Strong, "we've got to get back!"

"You ain't going nowhere, Strong," snarled c.o.xine behind him. "I've been waiting a long time for this!" He suddenly struck the Solar Guard officer with a heavy rock and Strong slumped to the ground unconscious.

Before Astro could move, c.o.xine smashed him to the ground with a blow on the back of the neck. They both lay deathly still.

Then, as the atomic bombardment of the penal asteroid continued, the giant s.p.a.ce criminal jumped into the jet car and sped away.

CHAPTER 11

"Fire!" bawled Major Savage to his crew of gunners.

At the other end of the field one of the remaining two undamaged rocket destroyers blasted off to battle the invading s.p.a.ceship.

Tom and Roger had been on a tour of the great central tower with Major Savage when the attack came and had been ordered to find safety in the open fields. The major knew the tower would be one of the first targets.

Sprawled on the ground behind a bunker, they saw the major, his s.p.a.ce jacket torn from his back, standing in the middle of the field, quietly issuing orders to scarlet-clad s.p.a.cemen, desperately trying to organize the penal asteroid's defenses.

The s.p.a.ceship, which had somehow managed to penetrate the tight radar warning screen around the prison, had struck with merciless precision.

Again and again, its atomic blasters had found the most important installations and had wiped them out. The first target, after the tower had been shattered, was the underground launching ramps for the asteroid's small fleet of rocket destroyers. But even after a direct hit, the guards were able to ready two ships to fight the attacking s.p.a.ceship. The first was already diving in, her small one-inch blasters firing repeatedly.

Suddenly, Lieutenant Williams, in command of the second ship, came racing up to Major Savage, to report that his radarman had been hit and the ship couldn't blast off.

"Here's where I get into the act!" Roger jumped up immediately, and with a brief "So long, s.p.a.ceman" to Tom, raced off to join Lieutenant Williams.

"s.p.a.ceman's luck," yelled Tom as the officer and the cadet ran toward the waiting ship.

Looking skyward again, Tom saw the first destroyer diving toward the attacking s.p.a.ceship, trying to get in range with her lighter armament.

Suddenly there was a burst of brilliant light. The lighter ship had been completely destroyed by a direct hit.

Sick with horror, Tom looked away and watched the ship Roger had joined blast off under full acceleration. It roared s.p.a.ceward in a straight line, disappearing at incredible speed.

Meanwhile, the invader continued to blast relentlessly.

One--two--three--four--automatic reload--one--two--three--four, reload.

Over and over, firing at seemingly peaceful fields of gra.s.s, only to strike an armory, s.p.a.ce cradle, or supply depot buried underneath the ground. Suddenly it changed its course and trained its guns skyward. Tom looked up and saw a tiny flyspeck roaring straight down at the ship. It was Lieutenant Williams' rocket destroyer, with Roger on the radar bridge, in a suicidal attempt to destroy the invader. But the larger ship was ready. The two forward blasters opened fire. A flaming ball of light exploded near the stabilizer of the destroyer and it fell off course to float helplessly in free-fall orbit around the asteroid. Still lying on the ground, Tom sighed with relief. At least Roger was all right.

Then the young cadet saw the invading s.p.a.ceship move away from the area around the tower toward the horizon not too far away on the small planetoid. He followed it with his eyes and saw it suddenly land near a cl.u.s.ter of white prisoner huts. Tom gasped as the reason for the attack became clear.

"Major! Major! Major Savage!" he called as he raced across the field.

But the major was nowhere to be seen. A guard carrying a medical kit hurried past him and Tom grabbed him by the arm.

"Major Savage! Where is he?"

The guard pointed to a near-by stretcher and Tom saw the unconscious figure of the major sprawled on the plastic frame.

"But--but the prisoners are getting away!" yelled Tom.

"I can't do anything about it. I've got wounded men to care for!" The man jerked away and disappeared in the smoky, choking dust.

The curly-haired s.p.a.ce cadet, his face blackened from the smoke, his lungs crying for fresh air, started across the blast-pitted field, looking for help. But there was none to be had. Suddenly he wheeled in the direction of the s.p.a.ceship and started to run toward it.

As soon as the young cadet had left the smoking area around the wrecked tower, he realized that it was the only section of the small satellite that had suffered attack. Ahead, he could see the prisoners in their white suits crowding around the stabilizer air lock of the invading ship.

Tom dropped to his stomach and watched the knot of men. Suddenly the air-lock portal slid open. There was a loud cheer and the prisoners began scrambling aboard.

Tom knew he would have to move fast. Taking a dangerous chance, he rose to a half-crouch and dashed to one of the small white huts only a hundred feet away. With a final glance at the thinning crowd of escaping men around the ship, he ran straight for an open window, diving headlong through it.

Inside, Tom waited breathlessly for a shout or warning that he had been seen, but none came. He glanced through the window and saw that only seven or eight men remained outside the port. He turned away quickly and began searching the hut.

He found what he was looking for rolled up on the bed where its owner had used it as an extra pillow. He shook out the prison suit of white coveralls, stripped off his own blue cadet's uniform, and hurriedly put on the distinctive prison gear. It was a little large for him and he rolled up the sleeves and trouser legs, hoping no one would notice in the excitement. Then, with a deep breath, he stepped out of the hut into full view of the prisoners still left at the air lock.

"Hey, wait for me!" he yelled, running for the ship.

The men paid no attention in their haste to get aboard the ship. When Tom reached the air lock, there were only two left. He slapped the nearest man on the back.

"Pal, I've been waiting for this a long time!"

"Yah," the man answered, "me too!" Then he looked at Tom closely. "Say, I've never seen you around here before!"

"I just got in on the supply ship last week. They kept me in the tower for a while," Tom replied.

"Oh, well," said the man, "they ain't keepin' anybody there anymore!"

"Come on you guys," snarled a heavy-set man in the air lock above them.

"We ain't got all day!"

Tom looked up, and without being told, he felt he was looking into the face of Bull c.o.xine. And when the other prisoner spoke, he was certain.