A group of Catholics go to a mental institution to perform exorcism in the murderer George Viznik (Brad Greenquist). Father Lareaux (Sir John Hurt), Deacon John Townsend (Elias Koteas), Father Frank Page (Brian Reddy), and the teacher Maya Larkin (Winona Ryder), who was possessed and exorcised in the past, unsuccessfully try to exorcise the man and Father Lareaux is deeply affected and falls into a coma. Maya brings the Viznik's coded writings and after deciphering it, she concludes that the writer Peter Kelson (Ben Chaplin) might be the Antichrist to be incarnated by Satan. She seeks him out but the atheist Peter, who has been raised by his uncle Father James (Philip Baker Hall), does not believe in her. But when strange things happen to him, Peter meets Maya and they investigate together the chance to save his soul.