"It's in," he said, and then added, "I would like to ask you a few questions, Barret."

"Sorry, haven't got time!" replied Barret curtly as he tried to brush past Strong. But the young captain grabbed him by the arm and spun him around.

"Make time!" he snarled. "I want the straight story about that so-called test flight!"

Barret glared at Strong. "I suggest that you let go of my arm, Captain," he threatened, "or I will be forced to bring charges of assault against you!"

Realizing an open fight would be useless, Strong released his grip on the man's arm and turned away quickly. Barret's mocking laugh echoed in his ears as he stepped on the slidewalk and glided away toward the Academy. Behind him, the big hangar buzzed with the sound of men working in high gear again. The mighty ship and its specially designed equipment seemed at last to be ready for testing. But Strong felt none of the excitement. It mattered little to the Solar Guard captain whether the project was a success or failure. His thoughts were of the three cadets in his unit, who were, first and foremost, his responsibility.

With double guards around the hangar area and even tighter security restrictions than before, the unknown saboteur was unable to attack the precious ship again. But he struck elsewhere. The single track monorail that Barret had run into the area was blocked by an explosion in the mouth of the tunnel. Nearly a thousand tons of rock and earth had fallen on the hangar side, blocking delivery of vital equipment.

With powerful earth-moving machinery, the tunnel was cleared of the heavy rocks and dirt, and all that remained was a general cleaning up, and the enlisted man's work gangs had been assigned to that job.

Nearly a hundred tough, battle-scarred spacemen from the enlisted ranks of the Solar Guard worked in the area, stripped to the waist, their bodies burned brown from the sun. Sent to the work gang for petty offenses, rather than for criminal acts, the enlisted men as a whole did not mind the work. They were under guard, watched by a squad of Space Marines armed with paralo-ray guns, but there was no attempt to make the men feel as if they were criminals. Most of the sentences were short, usually running from five to thirty days, with some extreme cases serving as long as three months. But no one had ever remembered a Space Cadet working on the squad, and particularly for six months! It was an extraordinary situation and the guards, as well as the men on the work details, sympathized with Roger and Astro. They realized that nothing really serious had been done, or the boys would have been sent to the prison asteroid, where all true criminals were sent. So a true spirit of comradeship developed between the cadets and the enlisted men.

When Captain Strong arrived to speak to Roger and Astro, he found them in the tunnel, working as a team of a shoveler and a sweeper. Roger would sweep up a little pile of dirt and Astro would shovel it into a handcart nearby.

"All right, you Venusian pug!" bawled Roger. "Police the joint!"

Astro scooped up the little pile of dirt neatly and deposited it in the truck.

"Manning, what made the spaceship cross to Pluto?" he asked.

"To get to the other side of the universe," said Roger.

"All right," interrupted Strong. "If you two will cut out the comedy, I'd like to talk to you."

"Captain Strong!" yelled Roger. "Hey, fellas! Look!" He turned to the other men on the work gang. "We're special characters! See? We have visitors during working hours!"

Strong laughed with the others, and then motioning for Roger and Astro to follow him, walked to an isolated corner of the tunnel.

"How is it going?" he asked.

"Fine, sir," said Roger. "We have no complaints."

"Yeah," chimed in Astro with a grin. "The food is better here than at the Academy!"

"Give this Venusian bum a good kitchen and he'd go to the Rock!" Roger laughed.

Strong noted their lean, brown bodies and decided that a little work in the sun with a pick and shovel had done them good. But six months of it would interfere with their work at the Academy and could hold them back.

He told them of the work he had been doing to have their case renewed by the Solar Guard Review Board and asked them for any special details in their relationship with Barret that might lend weight to his plea for outright pardon, rather than just a commutation of sentence. He wanted it clear on their records that they had been accused unjustly, and that, therefore, their sentence was an error.

But neither Astro nor Roger could add anything to what the young captain already knew. He finally turned to leave, cautioning them both to stay out of trouble, especially Roger.

"Manning," he warned, "your mouth is your big weakness. I'm detailing Astro to make sure it stays closed!"

"You see?" gloated Astro. "You see who the captain trusts!"

"Listen, you big bum!" began Roger angrily, then stopped and grinned. "O.K., Captain Strong, I'll keep on the ball."

"You'd better," Astro interrupted, "or I'll stand you on your head!"

With a pat on the back, Strong left them. Just as he was about to leave the tunnel, Roger called after him:

"Have you heard anything about Tom, sir?"

"Not a word," replied Strong grimly. "So far as I know, he's still on Mars."

"A—a fugitive?" asked Astro.

"Yes, Astro. The Solar Guard is still looking for him."

Strong watched the two cadets turn back to their work dejectedly, and then, sighing with weariness, he headed back to the slidewalk. In the morning he would check the reports of the Security Section for word of Tom. Then he squared his shoulders determinedly. He would check them now!

He could not go to bed yet. Not while Tom was still missing and while Astro and Roger were on the work gang. He would not sleep until they were free and the Polaris unit was together again out in space!

Tom Corbett was also unable to sleep. He had spent the night in the village hotel tossing and turning, his mind seething with plans to aid Roger and Astro.

Finally, at dawn, he got up and sneaked out of the hotel. Avoiding the convenience of the monorail, he struck out on foot over the rugged countryside for Space Academy. He had a plan, but the plan required that he talk to Roger and Astro first, and then to Captain Strong, but it had to be done secretly. He realized that his knowledge of the identity of the saboteur would be a more effective weapon if everyone still believed he was on Mars.

After getting close enough to the Academy to use the slidewalk system crisscrossing the huge area, he loitered on the crowded platforms which connected the hangar, the Academy, and the spaceport. He kept his coat collar high and his civilian hat pulled low over his eyes.

He was on the main slidewalk, moving toward the Tower building, when his eyes picked out the familiar close-cropped blond hair of Roger and the unmistakable bulk of Astro on the walk leading to the hangar. Changing at the slidewalk intersection, he took off after them, hoping he would not be noticed in the crowd of civilian workers. Roger and Astro were carrying tools over their shoulders and were lagging behind the main body of workers moving toward a huge tunnel opening. Tom saw his chance and moved up quickly beside them.

"Keep walking and don't show surprise!" he whispered sharply.

But it was too much to ask. Astro and Roger jumped in surprise and let out involuntary shouts of joy, which attracted the attention of the guards. They noticed the stranger in civilian clothes and stared at him.

"Tom!" exclaimed Roger. "What the devil are you—?"

"Sh!" hissed Tom. "We haven't got much time." He saw one of the guards turn and stare at him. "Listen to me," he continued quickly. "I've got important dope about the saboteur!"

"How?" gasped Astro.

"Never mind," replied Tom. "Now, to nail him, I've got to get him into the act! I need proof!"

"But who is it?" asked Roger.

"I can't tell you now. Here comes the guard. Are you going to be working around here long?"

"At least another three days," said Roger. "But who—?"

Roger noticed the guard move up to them and he suddenly straightened up and snorted derisively, "Yeah. But why a guy should want to join the Solar Guard is more than I can see. You must be wacky, mister!"

He and Astro walked away, and after a hesitant look at Tom, the guard followed the two cadets. Tom boarded the slidewalk heading back toward the Academy. So far, so good. He knew where his unit mates were, but up ahead, in the gleaming Tower of Galileo, was his second target, Captain Strong. His skipper had to listen to him, had to be sympathetic and help him catch the saboteur. It was the only way Tom could clear his own name and free Roger and Astro.