ere seeing, that invisible eyes were upon him.

The blocks were massive when he drew near to them. They were buried in
the sand, their sides like mirrors, their edges true and straight.
"Crystals," Rawson tried to tell himself, but he knew they were not.

Gun in hand, he moved among the great rocks. Open sand lay beyond,
running off at a steeper pitch to make a throat--a smaller pit in the
great pit of the crater itself. Rawson noted it, then forgot it as he
stooped for something that lay half hidden, its protruding end shining
under the light of the stars, as he had seen it gleam before at the
derrick's base.

He snatched up the metal tube, noting the lava tip, and that it was
like the one Smithy had found in the ghost town. The tube, clearly,
was part of some other mechanism, and Rawson realized with startling
suddenness that he was holding in his hand the jet of a
flame-thrower--the same one, perhaps, that had almost sent him to his
death.

The thought, while he was still thinking it, was blotted from his
mind. He was thrown suddenly to the sandy earth; the sand was slipping
swiftly from beneath his feet; he was scrambling on all fours, clawing
wildly for some anchorage that would keep him from being swept away.

* * * * *

He touched a corner of shining stone, drew himself to it, reached its
slanting side, then scrambled frenziedly to the top and threw himself
about to face the place of slipping sands. But where the sand had
been, his wildly glaring eyes found only a black hole--a vertical
bore, like the ancient throat of the volcano; and this, like the
tunnel in the sand, was lined with smooth and glistening glass.

It was black at first, a yawning, ominous maw, till the polished sides
caught a reflection from below and blazed red with the glare of hidden
fires.

No time was needed for Dean's quick searching eyes to grasp the
meaning of the change. Whatever had menaced the camp had set this
trap. He swung sharply to leap from the block, but stopped at the
sight of Smith's chunky figure coming slowly across the sand.

"Back!" he shouted. His voice was almost a scream, shrill and
crackling with excitement. "Get back, Smithy! I'm coming!"

* * * * *

He would have leaped. Below the block the sand bulged upward as a
yellow animal-thing came clawing up into the night. Dimly he saw
it--saw this one and the others that must have been hidden in the