d turned that the eyes might look backward as if some danger
threatened from below.

"I've got a ship," Chet assured her. "God knows who you are or how you
got here, but it's all right now. We'll leave."

He had regained his grip upon one of those slender hands and was
preparing to swing her up to the top of an incredibly high rock. Her
scream checked him and sent his one free hand to the detonite pistol at
his waist.

"Behind you!" she cried. "Look back! They have come out!"

The crater-pit behind and below them was black with the inky blackness
of smooth, fire-formed rock. Its many facets were smooth and polished;
they made mirrors, many of them, for the earthlight reflected from the
crater mouth. They served to diffuse this dim light and throw it again
upon the monstrous blacknesses that were swarming from below.

"Men!" thought Chef in one instant of half-comprehension. Then, as he
saw the chalk-white bodies, the dead and flabby whiteness of their faces
from which red eyes stared, he revised his estimate; here was nothing
human.

The pistol was in his hand, but as yet he had not fired. Only the terror
in the girl's voice had told him that these were enemies; he waited for
a closer view or for some direct attack, and needed to wait but a
moment.

Only an instant after he had seen, the chalk-white bodies clustered
below were in motion. They came leaping up the smooth expanses of rock,
and they were obscured at times as if by black curtains that were drawn
across their bodies. Then they would flash out again in dead-white
nakedness.

* * * * *

It was uncanny. Chet had a feeling that they were wrapping themselves in
black invisibility. Only when a score of the white things threw
themselves out into space did he know the truth.

Out and upward they sprang, to soar above Chet's head and land on the
slope above. All escape was cut off now; but it was not this thought
that held Chet motionless for that moment of horror. It was the glimpse
he had had against the light of the crater mouth of beating, flailing
wings that whipped the thin air above him; of curved claws; and of long,
horrible tails that might have belonged to giant rats. And the demoniac
cries that the thin air brought him were no more suggestive of devils
unleashed than were the leathery wings and the fleshy tails of the
beasts.

Yet it was not this alone that stunned the mind of the master pilot, but
the horrible