This overlooked film is based on the strange best seller The Manitou, a 1976 novel by British writer Graham Masterton, the former editor of the U.K. edition of Penthouse and occasional sex manual scribe.

Part of the “strange things happening to normal people” genre of 1970s horror, The Mantiou is a truly bizarre stunner starring, of all people, Tony Curtis as a psychic who has to help his girlfriend with the “tumor” on her neck. As it turns out, the tumor contains the living body of a 400-year-old Native American shaman attempting to reincarnate himself through her in order to take revenge for the extermination of his people. Cronenbergian in its body horror but totally camped out, The Manitou is definitely the best horror movie based on a book you haven’t seen.