Nancy Walker (Sandra Dee) is the virginal coed at a California university slated to mate with the devil himself. Wilbur Whateley (Dean Stockwell) is the son of the devil who recruits the unknowing Nancy for the Satanic ritual. Sam Jaffe is his addled relative, and Ed Begley plays the college dean Dr. Armitage. This mystery is taken from the novel by H.P. Lovecraft. Wilber's invisible supernatural brother devours a helpless damsel (Donna Baccala), a victim of her own curiosity in this unspectacular horror film.