Legion is a 1983 horror novel by American writer William Peter Blatty, serving as a direct sequel to his landmark 1971 novel The Exorcist. The story brings back Lieutenant William F. Kinderman, the thoughtful detective from the original book, and places him at the center of a disturbing new mystery. A series of gruesome murders in Georgetown bear the unmistakable signature of a deceased serial killer known as the Gemini, forcing Kinderman to confront the terrifying possibility that something beyond the natural world is at work.
The novel blends the conventions of a police procedural and a whodunnit with profound theological horror. As Kinderman investigates, the trail leads him to a psychiatric ward and a catatonic patient who seems to be the nexus of an ancient, malevolent force. Blatty uses the framework of a murder mystery to explore weighty themes of faith, suffering, and the nature of evil, questioning whether the horrors humans inflict on one another can be separated from the demonic.
Legion was the subject of a notable legal dispute when its publisher sued The New York Times for excluding it from their bestseller list, alleging the omission was deliberate and cost the book significant sales. Though the lawsuit was ultimately unsuccessful, it drew attention to the influence of the Times list and cemented the novel's place in literary history. The book remains a celebrated, cerebral entry in the horror genre, praised for its philosophical depth and chilling atmosphere.