This episode is based on a story by Robert Barbour Johnson of the same name, published in the June-July 1939 issue of Weird Tales. One of the most significant changes from the original story is that the men working below begin to take on the characteristics of the creatures. Had this been retained onscreen, this may have made better sense of the twist ending.
Alan Howarth, who scored this episode, and director Debra Hill previously worked together on Halloween II and Halloween III: Season of the Witch. Alan Howarth co-composed the music for both films (and scored the subsequent three films solo) while Debra Hill produced them (as well as having co-written Halloween II). Both also served the same capacity on Escape from New York.