p."

On the balcony Tom and Astro looked at each other.

"They're responsible for what's happened here on Titan!" whispered Tom.
"They have been sucking off oxygen from the main pumps supporting the
force field."

"Come on, Tom," growled Astro. "My fist is just itching to make contact
with a couple of no-good chins."

"Not so fast! We still don't know where they've got Roger."

"You want to keep on following them?" asked Astro.

"At least to their ship," Tom replied. "Then we can notify Captain
Strong and he can track them in the _Polaris_. If we barge in on them
now, we'll just get the satisfaction of knocking their heads together
with no guarantee of any information." The young cadet turned to the
door. "We'll sneak up the tunnel a way and then follow them out."

"Hurry!" said Astro. "Here they come." Quent, carrying one of the
instruments, had started up the steps to the balcony.

Tom grabbed the latch and pushed up but the door would not open. "Give
me a hand, Astro, quick!" he called.

Astro grabbed the latch and heaved his bulk against the door. Suddenly
he stepped back dumfounded, holding the latch in his hand. It had
snapped off.

Just at that moment Brett looked up and saw them. He shouted a warning
to Miles, who dropped the instrument he was carrying and pulled out his
ray gun.

"Just stand where you are!" he snarled, leveling the gun at them.

Tom and Astro stood quietly, hands in the air.

"How in blazes did they get here?" Brett cried.

"They must have followed me," said Miles. "They certainly couldn't have
known about this place."

"But how did they get past the trap?" Brett persisted, still amazed and
shaken by the unexpected appearance of the cadets.

Astro snorted his contempt. "You must think we're a couple of prize
space jerks," he growled. "You can't even kill a mouse with that thing
now."

"Let's cut the talk," said Miles. "What do we do with them?"

"Freeze them!" snapped Brett. "No telling how long they've been here and
how much they know."

"We know enough to put you on a prison asteroid," challenged Tom.

"Freeze 'em, it is," said Quent. "We'll get the ship loaded and decide
what to do with them later."

He pressed the trigger on his ray gun. There was a harsh crackling sound
and Tom and Astro stiffened into immobility, every nerve and muscle
deadened. With the exception of their hearts, and sense of seeing and
hearing, they might have been dead men.

Laughing to the