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. The moon door had closed!

O’Keefe took a stumbling step toward the barrier behind us. There was no mark of juncture with the shining walls; the slab fitted into the sides as closely as a mosaic.

“It’s shut all right,” said Larry. “But if there’s a way in, there’s a way out. Anyway, Doc, we’re right in the pew we’ve been heading for⁠—so why worry?” He grinned at me cheerfully. The man on the floor groaned, and he dropped to his knees beside him.

“Marakinoff!” he cried.

At my exclamation he moved aside, turning the face so I could see it. It was clearly Russian, and just as clearly its possessor was one of unusual force and intellect.