While filming a haunted asylum in St. Luis, Missouri, documentary filmmakers uncover a secret diary of the infamous 1949 exorcism of a 13 year old boy possessed by the devil that later inspired the book and movie, “The Exorcist”. For the first time ever, investigate the real Exorcist house and the infamous Haunted Boy’s bedroom where this horrific exorcism occurred. Exclusive interviews with the real Exorcist’s and Haunted Boy’s blood line. This is the untold story of “The Exorcist.”