angar
had been moved inside, with all but a few of the smaller ones remaining
outside. The secret work inside the hangar was advancing rapidly, but
this did not enter into the thoughts of the three cadets of the
_Polaris_ unit, nor of the _Capella_ unit. The harsh discipline
instituted by Tim Rush and the extra study necessary for the end-of-year
exams had forced the cadets into a round-the-clock struggle not only to
keep awake but to make the class promotion lists.

Roger paced off the required distance, wheeled smartly, and in so doing
came face to face with Astro, who was patrolling another side of the
hangar.

"I just saw Firehouse," said Astro quietly. "Did he catch you goofing?"

"Yeah," growled Roger. "I found a kitten and he walked up just as I was
holding it."

Astro grinned. "I wouldn't be surprised if that pocket-sized giant
didn't send that cat down there to tempt you."

"How's Tom?" asked Roger. Astro, in his patrol, came in contact with
both unit mates.

"Sleepy. He's having a tough time with that chapter on space law. He
didn't sleep at all last night."

"He better keep awake," said Roger. "That little fireman's got his
rockets hot tonight. He'll blast Tom sure if--"

"Wait a minute," said Astro suddenly, looking off into the darkness.
"What was that?"

Roger spun around, his rifle in his hands, ready to fire. "What is it?"
he asked.

"I don't know," replied Astro in a whisper. "I thought I saw something
move inside the hangar." He pointed to a large window. "Sort of a shadow
against the frosted glass."

"Are you sure?"

"Of course I'm sure."

"I'll investigate. You get Tom and call Firehouse."

"Right," replied Astro, and raced down the path, alongside the hangar.

Grasping his rifle firmly, Roger inched toward a nearby door. He opened
it a crack, then flattened himself against the wall and watched Astro
run toward the other end of the hangar. He saw the big Venusian say a
few quick words to Tom and then rush off toward the guardhouse and the
communicator. Tom waved to Roger, indicating that he would enter the
opposite door of the hangar.

Roger dropped to his hands and knees and poked his head through the open
door, peering around from one end of the huge dark chamber to the other.
Then, taking a deep breath, he rose and stepped quickly inside. He
closed the door behind him and stood still, listening for some sound.

Suddenly there was a flash of light from the opposite wall. Roge