The terror begins unobtrusively. Noises in the attic. In the child's room, an odd smell, the displacement of furniture, an icy chill. At first, easy explanations are offered. Then frightening changes begin to appear in eleven-year-old Regan. Medical tests fail to shed any light on her symptoms, but it is as if a different personality has invaded her body.Father Damien Karras, a Jesuit priest, is called in. Is it possible that a demonic presence has possessed the child? Exorcism seems to be the onlyanswer...