The Exorcist was one of the most successful horror movies of all time, grossing almost half a billion dollars at the box office. It was based on a real-life exorcism in 1949 in Maryland, USA, in which a priest claimed to have exorcised a demon from a thirteen-year-old boy whose family reported poltergeist activity. The ordeal lasted almost four months, with various priests reporting that the boy spoke in Latin, claimed to be a demon, and displayed ‘superhuman' strength. Using the diary kept by one of the priests, we investigate the disturbing ordeal the young boy went through.The documentary also explores the increase in exorcisms following the film's release, using actual footage of a modern day exorcism, and explores the work of a leading neuroscientist who has used magnetic field technology to reproduce the sensation of ‘possession' in normal people.