Country vicar Merrily Watkins is in training to be an exorcist, or "deliverance counselor," for the Church of England. Although guided by the sardonic, no-nonsense Reverend Huw Owen, Merrily contends with self-doubt in her tough new role. When Merrily is called in to consult on a grisly murder investigation, the inexperienced exorcist finds herself battling supernatural terrors that threaten to overwhelm her.