As I thrust my hands against it there came at my back a snarl and an oath and Larry staggered under the impact of a body that had flung itself straight at his throat.

He reeled at the lip of the shallow cup at the base of the slab, slipped upon its polished curve, fell and rolled with that which had attacked him, kicking and writhing, straight through the narrowing portal into the passage! Forgetting all else, I sprang to his aid.

As I leaped I felt the closing edge of the moon door graze my side.

Then, as Larry raised a fist, brought it down upon the temple of the man who had grappled with him and rose from the twitching body unsteadily to his feet, I heard shuddering past me a mournful whisper; spun about as though some giant's hand had whirled me-- The end of the corridor no longer opened out into the moonlit square of ruined Nan-Tauach.

It was barred by a solid mass of glimmering stone.