While filming a haunted asylum in St. Louis, 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. Utilizing hi-tech paranormal gadgetry along with a legion of supernatural experts, they search out to capture the scariest entity known to man, the Unholy Ghost. Nothing you have ever seen or heard before gets you closer to the ungodly truth of what really happened in this most terrifying, best selling story of all time! For the first time ever, investigate the real Exorcist house and the infamous Haunted Boy's bedroom where this horrific exorcism occurred. Battle demons while exploring ancient churches and asylums with the last surviving priests. Witness never-before-seen video, historical events, paranormal evidence from the actual case files. Exclusive interviews with the real Exorcist's and Haunted Boy's blood line. This is the untold story of The Exorcist, a chronicle of true events based on the priest's secret diary the world was not to see, Until Now!