Thomas B. Allen

Publication and film His most famous book to date was Possessed. It is a retelling of the true story of a teenage boy (whom Allen identified by the pseudonym Robbie Manheim) from Mt. Rainier, Maryland, who went through the rite of exorcism in 1949. Allen tracked down the sole survivor of the team that performed the exorcism, Father Walter Halloran, as well as a copy of the diary kept by the team leader, Father William S. Bowdern. A diary authored by Father Raymond J. Bishop, S.J. is the primary source of documentation. Father Raymond J. Bishop, S.J enlisted the assistance of the other Jesuits. It was upon this case William Peter Blatty based the events of his novel, The Exorcist. First published in hardcover in 1993, the book was reïssued as a revised paperback in 2000 to coïncide with the release of a made-for-cable film Possessed starring Timothy Dalton as Father Bowdern. Since publication of the book, Allen had been a frequent guest on talk shows, entertainment shows, and history shows that discuss exorcism in general, demonic possession, and the case his book details.

Speaking in 2013, Allen "emphasized that definitive proof that the boy known only as 'Robbie' was possessed by malevolent spirits is unattainable. Maybe he instead suffered from mental illness or sexual abuse — or fabricated the entire experience." According to Allen, Halloran also "expressed his skepticism about potential paranormal events before his death."

Criticism Allen's Possessed has been criticized by Mark Opsasnick, who wrote that it contained questionable or inaccurate material, such as misidentifying the location as Mount Rainier, Maryland, rather than Cottage City, Maryland.