his charts.

"Here he is, Captain," said Brooks. "The other two are sealed up in the
air lock like sardines!"

Coxine nodded and faced Tom, a thin smile on his face. "I told you I
would get the recognition signal, Corbett," he said. "And I will!"
Coxine walked over to a large valve on the after bulkhead and tapped the
needle indicator right beside it. Satisfied, he turned back to the
cadet.

"In two hours," began Coxine, "we'll be within range of the Ganymede
garrison and its radar. It takes exactly eight turns on this valve to
bleed the air out of the air lock where your two buddies are. So, every
fifteen minutes I'm going to ask you for the recognition signal, and
every time you say no, I'll turn the valve once. By the time we get
close enough to Ganymede to be picked up on their radar, you'll either
have given me the signal or your buddies will be dead!"

Tom stood listening to Coxine, his blood boiling at the giant spaceman's
cruelty. Suddenly he tore across the control deck and made a dive for
Coxine's neck. But the big man met him coming on and with a powerful
slap of his hand sent the boy sprawling back across the deck.

"You're a good man, Corbett," said Coxine, standing over the fallen
cadet, "but you're a _little_ man, and a good big man can lick a good
little man any time!"

Brooks and the crewmen laughed loudly as Tom dragged himself to his
feet.

"Well, do I get the signal?" demanded Coxine. "Or do your buddies get a
little less air?"

Standing unsteadily on his feet, with four paralo-ray guns trained on
his body, Tom thought quickly of Roger and Astro, alone in the darkness
of the air lock, soon to be clawing their throats for air; of the
merciless attack on the prison asteroid; of the helpless ships Coxine
had looted. All these things and more flashed through the curly-haired
cadet's mind as he weighed his life and the lives of his unit-mates
against an attack that would devastate the small satellite of Jupiter.
Tom could see through the pirate's demand for the recognition signal.
Once inside the Ganymede radar screen, he could attack the Solar Guard
garrison and wipe it out before it could raise a ship in defense.

"Well?" demanded Coxine, placing his huge hand on the valve.

Tom knew that if he could stall long enough, the signal aboard the
_Polaris_ might be picked up by the Solar Guard. Roger and Astro were in
good physical condition. They could conserve their energy as soon as
they disco