Reverend Cotton Marcus arrives on the rural Louisiana farm of Louis Sweetzer, expecting to perform just another routine ritual. An earnest fundamentalist, Sweetzer has contacted the charismatic preacher as a last resort, certain his teenage daughter Nell is possessed by a demon who must be exorcised before their terrifying ordeal ends in unimaginable tragedy. But upon arriving at the already blood drenched family farm, it is soon clear that nothing could have prepared him for the true evil he encounters there.