Country vicar Merrily Watkins (Anna Maxwell Martin, The Bletchley Circle, Death Comes to Pemberley) is in training to be an exorcist, or 'deliverance minister, for the Church of England. Although guided by the sardonic, no-nonsense Reverend Huw Owen (David Threlfall, Shameless, Hot Fuzz), Merrily contends with self-doubt in her tough new role. Her faith deeply shaken by her husband's recent death, she also struggles to raise her teenage daughter on her own. 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.