Inspired by a 1949 article in The Washington Post in which a Catholic priest recounts his experience performing the ritual of exorcism on a young child, William Peter Blatty's groundbreaking novel details the demonic possession of eleven-year-old Regan MacNeil. When neither medical professionals nor psychiatrists can come to Regan's aid, her mother enlists the assistance of two priests. Overwhelmed but determined, they endeavor to rescue Regan from an unspeakable fate. To do so, they must face a series of terrifying moments that will test not only their strength, but the very core of their faith.