 The university student Walter Gilman moves to a very low-budget room in an old house. He becomes close to Frances Elwood, his next door neighbor, and her baby son Danny after saving them from a huge rat. While studying for his thesis, Walter listens to noises in the first floor, and finds the tenant Masurewicz praying and hitting his head on a chair. The old man advises him about a rat with a man s face and a witch that would be after him, and offers a crucifix for his protection. Walter ignores the advice, and has nightmares along the night. When Frances asks Walter to be the babysitter of Bobby for a couple of hours, Walter is lured by the witch, who pretends to be Frances, and he is marked on his back. Later he realizes that the evil witch is Keziah Mason and the rat is her assistant Brown Jenkin, and they want him to sacrifice Bobby in an ancient ritual to the devil.