Scarification and speaking backwards? Save your soul! An exorcism must be performed. Scare the devil out of them all with the Exorcist Regan Adult Costume! The Exorcist is a 1973 American horror film directed by William Friedkin, adapted from the 1971 novel of the same name by William Peter Blatty and based on the exorcism case of Robbie Mannheim, dealing with the demonic possession of a young girl and her mother's desperate attempts to win back her daughter through an exorcism conducted by two priests.