The Ninth Configuration
…William Peter Blatty, in his directorial debut. It is the second installment in Blatty's "Trilogy of Faith" after The Exorcist (1973), and followed by The Exorcist III (1990). The film is based on Blatty's 1978 novel The Ninth Configuration, which was itself a reworking of his 1966 novel Twinkle, Twinkle, "Killer…