Some human explorers ^in a deserted ancient city on Mars^ [on a dying world] who are driven to take shelter in subterranean vaults by a strange, crawling, mat-like monstrosity called the vortlup. The vaults are evidently of mausolean nature, and contain the mummies of an ^ancient Martian^ [unknown] race, some of which lack the upper portion of the head. The explorers become separated in the dark, winding passages, and one is lost from the others. They hear a muffled cry at some distance, followed by silence; and going in the direction of the cry with their flashlights, meet a terrible sight — the body of their comrade which still walks erect, with a great black, slug-like creature attached to the half-eaten head. The thing is controlling the corpse ^which passes its friends, enters another catacomb, and removes a heavy boulder from the mouth of a deeper vault, beneath the direction of the slug^ [which attacks its former friends. One of them shoots the slug — which dissolves in dark viscous fluid — and the corpse falls]. Following, the others shoot the creature, which dissolves in a sort of liquid putrescence, and, at the same time, the animated corpse drops dead. Then, from the uncovered pit, there emerges a horde of the black monsters, and the men flee. They are not followed into the sunlight; and fortunately the vortlup has disappeared.

^xxx^ xxx was added by Smith.
[xxx] xxx was deleted by Smith.