Nancy Walker and Elizabeth Hamilton, two students who attend Miskatonic University and work in the school library, are putting away the Necronomicon , a rare book on the occult, after a lecture on the supernatural given by visiting professor Dr. Henry Armitage. Dr. Armitage discovers Wilbur Whateley memorizing ritual passages from the Necronomicon and is at first angry, but learns that Wilbur comes from nearby Dunwich, a village having a history of evil occurrences, and that Wilbur is the great-grandson of Oliver Whateley, who was hanged by the villagers as a demon. Nancy, finding herself attracted to Wilbur, offers to drive him home when he misses his bus. Later, in the old mansion where Wilbur lives with his grandfather, Wilbur drugs Nancy and sabotages her car, thus forcing her to stay for the night. (He plans to sacrifice her in a fertility rite in the hopes of gaining for himself contact with the spiritual world.) Nancy accepts his invitation to spend the weekend there, but her absence alarms both Elizabeth and Dr. Armitage, who learn that Wilbur's mother has been living in an insane asylum since giving birth to twins--Wilbur and a boy who has never been seen. Wilbur steals the Necronomicon from the library, kills a guard, and takes Nancy to the "Devil's Hopyard," a rocky hillside, for the ritual. Meanwhile, Elizabeth and Dr. Armitage arrive at the Whateley house; Elizabeth opens a locked door and is immediately devoured by an invisible creature, the Dunwich Horror (Wilbur's twin). The Horror escapes and ravages the countryside, intending to kill Wilbur. Eventually, Dr. Armitage confronts Wilbur and the monster at the Devil's Hopyard, and there Armitage utters a curse which sends both Wilbur and the Dunwich Horror up in flames.