head was directly in line with the
largest crater's irregularly broken top; and about it was the faintest
tinge of red.

For a moment the light flamed close; it seemed to be hovering about
the head of the silent, seated man. Then Rawson moved, looked past,
and found a true perspective for the phenomenon. One rugged cleft in
the rim of the crater's cup made a peephole for seeing within. It was
plainly red--the light came from inside the age-old throat.

* * * * *

"It's alive!" Rawson whispered in quick consternation. Almost he
expected to see billowing clouds of smoke, the fearful pyrotechnics of
volcanic eruption.

He sensed more than saw that Smithy had not turned his head. "Look!"
he was shouting by now. "Wake up, Smithy! Good Lord!"

He stopped, open-mouthed. The red glow had meant volcanic fires; to
have it change abruptly to a green radiance was disconcerting.

Green--pale green. Only through the gap, like a space where a tooth
was missing in the giant jaw, could Dean Rawson see the changed light.
Only from this one point could the view be had--there would be nothing
visible from the camp below. And as quickly as it had come all
thought of volcanic fires left him; he knew with quick certainty that
this was something that concerned him, that threatened, and that was
linked up with the other threatening, mysterious happenings of the
recent nights and days.

Still Smithy had not turned. Rawson felt one quick flash of annoyance
at his helper's dullness--or indifference; then he knew that Smithy's
dark-haired head was reached forward, that he was bending at a
precarious angle to stare below him into the valley. Then:

"They're there!" said Smithy in a hushed voice, as if someone or
something on that desert floor far below might hear and take alarm.
"Look, Dean. Where's your glass? What are they?"

* * * * *

His cautious whispering was unnecessary. Below them a thin line of
light pierced the darkness; another; then three more in quick
succession before the sharp crack of pistol fire came to the men a
thousand feet above. Rawson had snatched up his binoculars.

"To the left," Smithy was directing. "Off there, by the big casting.
Great Scott! what's that light?"

Rawson got it in the glass--a single flash of green that cut the
blackness with an almost audible hiss. It was gone in an instant while
a man's voice screamed once in fear and agony, o