A disturbed priest, who witness an occult ritual, thinks the people are possessed and start a private inquisition to exorcise the demons by torturing them to death.
Anna Elisabeth "Anneliese" Michel was a German woman who underwent 67 Catholic exorcism rites during the year before her death. She died of malnutrition, for which her parents and the priest who performed the exorcism were convicted of negligent homicide. She was diagnosed with epileptic psychosis and manic depression, and had a history of psychiatric treatment that proved ineffective.