the officer. He rammed the accelerator to the floor
and the small truck blasted through the streets as though shot out of
cannon.

In a few minutes the truck screamed to a halt in front of the building
and Strong leaped toward the door, followed closely by Sergeant Morgan
and the Space Marine lieutenant.

Strong found Walters before the telemetering board waiting impatiently
for some figures Dr. Joan Dale had sent him to be analyzed and
evaluated. He spun around when Strong entered the room at a dead run.

"Steve!" he exclaimed. "What's the matter? Anything happen to the
cadets?"

"We didn't find them, sir, but we did find something else. We--" Before
Strong could finish, the calculator began pouring out its answers.

"Excuse me, Steve! These figures could tell us why the screens are
failing."

"But I know why they're failing, sir!" shouted Strong.

"You know what?" exclaimed Walters.

As all the men in the room stared at him, Strong hurriedly told the
commanding officer what he had found, concluding, "I think the room I
stumbled into was used as a repair shop. But it was gas-free and pure
oxygen was coming out of the pipe I described."

"I see," said Walters grimly. "Let me check that against these figures."
He turned to the calculator and with the assistance of Joe Howard, Kit
Barnard, and the chief electronics engineer began studying the figures.

Strong paced up and down nervously. The faces of the technicians in the
room clearly showed the strain they had been under the past few days.
And when they heard the startling news Strong had delivered, there
wasn't one who didn't feel his fingers tighten into fists at Brett and
Miles' selfishness.

Walters straightened up and glanced at the faces of the men around him.
"Well, gentlemen," he said. "I think the figures speak for themselves."

There was a murmur of agreement. Walters turned back to Strong. "Those
figures prove conclusively that what you say is true. It is impossible
for the screens to collapse except from a vital leak--exactly such a
leak as you have described."

Walters turned and began to snap orders to the men around him. "I want
every available man sent out on the double. I want every inch of that
area searched for an opening to a mine shaft or anything that leads
underground. Take half the men off the spaceport detail."

"Shall we continue evacuation operations for the miners and their
families?" asked the young Space Marine lieutenant.