In August 1977, in a seemingly normal house in Enfield, North London a series of disturbing paranormal events have begun to take place. Reports of an unworldly presence making repeated attempts on the life of 11-year-old Janet Hodgson soon attracts the attention of paranormal investigator Maurice Grosse (Timothy Spall) who is convinced that the house is plagued by a poltergeist. With the attacks growing increasingly violent by the day Maurice will stop at nothing to protect Janet from these strange and dark forces.