your attempt to rationalize your fear will lend an interesting touch. Both of you will stand up, with your hands in the air, and precede me into this passage."
All this came out tonelessly and swiftly, quite as though it were a rehearsed speech. His hand slid over the wall beside him, and a black oblong widened in the oak paneling. I stood up.
"Do as he says, Ann," I said. "Maybe I can——"
"No, you can't," Keene interrupted, gesturing impatiently with his weapon. "You won't have the chance. Hurry up."
We went through the opening in the wall and Keene followed, touching a stud that flooded the passage with light. It was a narrow tunnel that slanted down through solid rock for perhaps ten feet to a steep stairway. He herded us down this, after sliding the panel shut.
"It's well hidden," he said, indicating metal sheathing—indeed, the entire corridor was lined with metal plates. "This lever opens it from within, but no one but me can find the spring which opens it from without. The police could wreck the house without discovering this passage."
That seemed worth remembering, but of little practical value at the moment. Ann and I went down the stairway until it ended in another short passage. Our way was blocked by a door of steel bars, which Keene unlocked with a key he took from his pocket. The passage where we stood was dimly lighted; there were several chairs here; and the space beyond the barred door was not lighted at all.
Keene opened the door and gestured me through it. He locked it behind me and turned to Ann. Her face, I saw, was paper-white in the pale glow.
What happened after that brought an angry curse to my lips. Without warning Keene swung the automatic in a short. vicious arc, smashing it against Ann's head.
She saw it coming too late, and her upflung hand failed to ward off the blow. She dropped without a sound, a little trickle of blood oozing from her temple. Keene stepped over her body to a switchboard set in the rock wall.
Light lanced with intolerable brilliance into my eyes. I shut them tightly, opening them after a moment to stare around apprehensively. I recognized my surroundings. I was in the cave of sacrifice, the underground den I had seen on the screen. Cameras high up on the walls began to operate as I discovered them. From various points blinding arc-lights streamed down upon me.
A gray curtain shielded a space on the far wall, but this was drawn upward to reveal a deep alcove. There was an object within that niche—a barrel-shaped thing ten feet high, studded with spikes, and crowned with a jewel that pulsed and glittered with cold flame. It was gray and varnished-looking, and it was the original of Keene's Aztec god.
Somehow I felt oddly reassured as I examined the thing. It was a model, of course, inanimate and dead; for certainly no life of any kind could exist in such an abnormality. Keene might have installed machinery of some sort within it, however.
"You see, Haviland," Keene said from beyond the bars, "the thing actually exists. I got on the trail of it in an old parchment I found in the Huntington Library. It had been considered merely an interesting bit of folk-lore, but I saw something else in it. When I was making Ape of God in Mexico I discovered the ruined temple, and what lay forgotten behind the altar."
He touched a switch, and light streamed out from the alcove behind the thing. Swiftly I turned. On the wall be-
