Twelve year old Regan MacNeil begins to adapt an explicit new personality as strange events befall the local area of Georgetown. Her mother becomes torn between science and superstition in a desperate bid to save her daughter, and ultimately turns to her last hope: Father Damien Karras, a troubled priest struggling with his own faith.
World War II soldier-turned-U.S. Marshal Teddy Daniels investigates the disappearance of a patient from a hospital for the criminally insane, but his efforts are compromised by troubling visions and a mysterious doctor.