In the early 1980s, do-it-yourself exorcists Ed (Patrick Wilson) and Lorraine (Vera Farmiga) Warren work to clear a youth (Ruairi O’Connor) accused of a brutal murder by proving that he was under demonic control when he committed the crime. They’re aided by the accused’s live-in girlfriend (Sarah Catherine Hook) and by an eccentric retired priest (John Noble) whose expertise on devil worship comes bound up with a distinctly fishy personality. Director Michael Chaves’ fact-based horror movie showcases rat-infested basements and contorting victims of possession but breaks little new ground. Along with predictable mayhem, the uneasy blending of nonscriptural mysticism — Lorraine is portrayed as clairvoyant — with explicitly Catholic piety and prayer as well as plot developments involving a wayward clergyman make this unfit viewing for youngsters. Some gory violence, mature themes including occult activity, brief sensuality in the context of cohabitation, a couple of profanities, a few milder oaths, at least one crude term. The Catholic News Service classification is A-III — adults. The Motion Picture Association rating is R — restricted. Under 17 requires accompanying parent or adult guardian.