The terror began unobtrusively. Noises in Regan’s room, an odd smell, misplaced furniture, and icy chill. Small annoyances for which Chris MacNeil, Regan’s actress mother, easily found explanations. The changes in eleven-year-old Regan were so gradual, too, that Chris did not recognise for some time how much her daughter’s behaviour had altered. Even when she did, the medical tests which followed shed no light on Regan’s symptoms, which grew more severe and frightening. It was almost as if a different personality had invaded the child.
Desperate, Chris turned from the doctors to Father Damien Karras, a Jesuit priest who was trained as a psychiatrist and had a deep knowledge of such phenomena as satanism and possession. Was it possible that a demonic force was at large? If psychiatry could not help, might exorcism be the answer?