ould not sleep and had sought
the open. This figure was going somewhere! It had a definite object in
mind!

Sheltering himself behind the hangars' bulk, Lance advanced as
stealthily as he could. Coming to the end one, he peered round its
blunt corner. Fifty yards ahead, crossing a stubbly stretch of open
ground, the mysterious prowler hurried onward.

* * * * *

The night was dark, the moon troubled by ragged bursts of listless,
heavy clouds. Lance bent almost double and left the shelter of the
black hangar. Feeling his way carefully, he followed the other.

Was this the unknown spy? The spy, going to transmit the news he had
overheard?

Lance muttered a curse. He had no weapon with him; the spy, if he were
a spy, would certainly be armed. But that didn't matter; it was merely
unfortunate. He must track the other down, at all cost.

For some minutes he crept on in this manner. The other kept hurrying
forward. Lance noted a clump of brush far ahead; the figure was
evidently making for this. And sure enough, as if acting directly on
Lance's thought, the dark form entered the patch of growth--and did
not come out on the other side.

Lance broke into a trot, eyes wary and alert for sign of his prey. At
any second he might be greeted by a salvo of bullets, and every fiber
of his lean body was taut.

As he approached the clump of brush he dropped to the ground, and came
finally to it on his belly. From a distance of about ten feet, he rose
and charged.

Expecting each moment to hear the spit of a revolver, he was more
alarmed by what actually did greet him.

Nothing. The patch of brush was empty!

"Well I'll be damned!" Lance murmured. "Where did he get to?"

He gazed around, bewildered. The growth of bush was about ten feet
wide. On either side the flat Nevada plain stretched away--empty. No
figure was visible.

Lance was utterly baffled. The fellow had vanished as if by magic.
Flown away into thin air!

* * * * *

The young captain stood quite still, listening, probing his puzzled
brain.

Then, like a cat, he dropped to the ground again, and pressed an ear
to it. For his ears had caught a tiny betraying hum.

A hum! There was a machine of some type near him. He listened
intently. The hum came from the ground on which he lay. There had to
be a trap-door.

Lance's fingers scrabbled around, and presently found what they looked
for.

He se