The Possession of Michael D. (1995)

Michael and Jenny want to start to live together but the presence of a dark force begins to destroy their happiness forever. Everything seems to focus on Michael who has terrible nightmares and who begins to adopt strange and violent personalities. When common medicine does not offer any solution the couple decides to consult a parapsychologist who discovers that Michael is possessed by a demon. But in order to help him and to exorzise the devil the experts first have to discover his dark secret which is hidden in his past.