thing has come up
here at the exposition that needs your immediate attention."

"That's quite all right, Steve," said the commander with a smile. "What
is it? Manning get into more trouble?"

"No, sir," answered Strong grimly. "I wish it were as simple as that."
He quickly related the details of the strange dirt cloud and his
suspicions of Wallace and Simms. Walters' expression grew serious.

"I'll get out an emergency bulletin on them at once, Steve. Meantime,
you have full authority to head an investigation. Use any service you
need. I'll confirm my verbal order with official orders at once. Get on
this thing, Steve. It sounds serious."

"I will, sir, and thanks!" said Strong.

"End transmission!"

"End transmission," returned Strong, flipping off the teleceiver and
turning to the ship's intercom. "Attention, power deck! Corbett, you and
Astro go back to the shack and give Roger a hand. I'm going to work with
the commissioner here setting up search operations."

"Aye, aye, sir," replied Tom from the power deck.

The two cadets hurriedly closed the power units and left the ship.

"Did you hear what Captain Strong said, Astro?" asked Tom. "Search
operations."

"I wonder what's up," the big Venusian remarked. "They don't set up
search operations unless it's awfully serious!"

"Come on," urged Tom. "Maybe Roger's found something."

They entered the shack together and Tom called out, "Say, Roger, Captain
Strong just spoke to Commander Walters at the Academy and--"

The curly-haired cadet stopped short. "Astro, look!"

"By the rings of Saturn!" exclaimed the big cadet.

The two cadets stood gaping at a huge hole in the middle of the room.
The wooden floor was splintered around the edges of the opening and
several pieces of the chemical feed-line equipment lay close to the
edge, with trailing lines leading down into the hole. They heard a low
moan and rushed up to the hole, flashing their lights down into it.

"Great galaxy!" yelled Tom. "Astro, look! It's a shaft! It must be a
thousand feet deep!"

"And look!" bellowed Astro. "There's Roger! See him? He's hanging there!
His foot's caught in that feed-line cable!"

The big cadet leaned over the hole and shouted, "Roger! Roger! Are you
all right?"

There was no answer from the shaft. Nothing but the echo of Astro's
voice.

CHAPTER 6

"Easy, Astro," said Strong, standing behind the big cadet. "Pull that
line up slowly and gently."

"Yes, si