A Satanist cult leader is burnt alive by the local church. He vows to come back to hunt down and enslave every descendant of his congregation, by the power of the book of blood contracts, in which they sold their souls to the devil.

The film is a study of Anton Szandor LaVey, leader of a cult of devil worshipers in San Francisco. He and his Church of Satan are shown performing a black mass, in which a nude woman serves as an altar and a boa constrictor wraps itself around a naked witch. Newsreel footage is included in which LaVey's neighbors are interviewed about the lion which he kept in his house until complaints resulted in the animal's removal to a zoo. The ideology of the Church of Satan is discussed--guilt rejection, sexual freedom, and self-indulgence.