According to the FAQ section (http://www.imdb.com/title/tt0070047/faq?ref_=tt_faq_3#.2.1.5) of the first movie "The Exorcist," William Peter Blatty wrote a book ("The Exorcist," published in 1971) after coming across the original diary written by one of the priests However, Blatty's 14 year old boy lived in Mount Rainier, Maryland, not St. Louis, Missouri. Mark Opsasnick, an investigative journalist, looked into the story that was originally reported in "The Washington Post" on August 20, 1949. He could not find the boy in Mount Rainier, but did find a boy fitting the description who lived in Cottage City, Maryland. The journalist concluded that the boy was suffering from mental illness and not demon possession. So, how do we end up in St. Louis, Missouri, with a 13 year old boy in an asylum?