"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, one scream that broke like brittle steel in the same instant that it began. Dean found the big casting in the circle of his glass. There were black figures moving near it; they were indistinct. He changed the focus--they were gone before he could get their images sharp. But the casting! Plainly he saw its great bulk that many men had worked to ease down to the sand. It was outlined clearly now until its edge became a blur, until the sand rolled in upon it, and its black mass became a circle that shrank and shrank and vanished utterly at the last. "It's gone!" Rawson shouted. "It sank into the sand! I saw it...." He was running for the car. A clamor of voices was coming from below; the sound died under the thunder of the car's exhaust as Rawson gave it the gun and sent the big machine leaping toward the waiting curves. CHAPTER V _The Attack_