Reverend Cotton Marcus is a fourth-generation evangelical minister who has many faithful believers in his work…but he's not one of them. After years of cheating believers out of their money by performing fake exorcisms, Cotton has a crisis of conscience and decides to come clean by filming a documentary exposing his fraudulent ways. The film crew travels to a rural Louisiana farm where they meet Louis Sweetzer, a devout fundamentalist who believes his teenage daughter Nell is possessed. Among other horrific things, Nell wakes up each day covered in the blood of another butchered farm animal - but without any memory of the deeds. Louis is certain Nell must be exorcized or this terrifying ordeal will continue. Cotton tries his usual tricks at first, but soon realizes that all his years of religious charades have not prepared him for what they actually encounter. He and the crew must find a way to save Nell before it is too late for her...and for them.