Barret called over the intercom from the
power deck.

"Here comes number two," said Professor Hemmingwell excitedly, and began
to repeat the process to draw the approaching projectiles back into the
ship.

One after another, five projectiles were taken aboard successfully.
Then, as he worked on the sixth, the professor began to frown. He
rechecked his instruments and then shook his head, obviously disturbed.

"What's the trouble?" growled Connel, noticing Hemmingwell's growing
nervousness.

"The homing ring on number six tube isn't working properly," replied
Hemmingwell. "I can't control the projectile."

"Any idea what's wrong?" the Solar Guard officer asked.

"The settings on the ring must be wrong." The professor picked up the
intercom mike. "Dave," he called, "check in!"

"Yes, sir?" replied Barret immediately.

"Did you check the settings on all the rings in the firing chambers?"

"Yes, sir," reported Barret. "They looked O.K. to me. Why don't you
check with Connel? He supervised their installation."

"That's true," said the major. "I'll go outside and look them over."

Connel turned on his heel and hurried to the air-lock chamber. Moving
with amazing speed for a big man, he donned the space suit in the
chamber while the pressure was being equalized. As soon as the air-lock
portal opened, he scrambled out on the hull and made his way forward to
the bulging firing chambers. Stooping over the empty tube of number six,
he examined the ring carefully and began to frown. Moving on to number
seven, his frown deepened. By the time he checked the rings of eight and
nine, his face was a grim mask of anger.

"Professor," he called into his helmet microphone, "check in."

[Illustration]

"Yes, Major," replied Hemmingwell from the control deck. "Have you found
the trouble?"

"I sure have," Connel growled. "It's sabotage! And now I think I know
who--"

Connel never finished. There was a sudden burst of power from the great
ship and the officer was hurled into space.

"Major!" cried Hemmingwell. "Barret! What have you done? Connel is
outside!"

"I couldn't help it, Professor," replied Barret from the power deck. "My
hand slipped and--"

"Don't talk!" shouted Hemmingwell. "Stop the ship!"

"I can't! The control is jammed!"

As the ship surged through space and the professor and Barret yelled at
each other over the intercom, three Space Cadets rose from their hiding
place in the hold of the ship.

Tom