Widowed vicar Merrily Watkins serves a rural town while learning the art of exorcism from clergyman Huw Edwards. She also tries to mend her relationship with her teenage daughter, Jane, who is coping poorly with the loss of her father. Then the police call upon Merrily to help with their investigation into the murder of a man by crucifixion.

Merrily is not convinced that Canon Dobbs’s death was a suicide. When a dead, mutilated crow is found on a church altar, she begins to believe the strange events point to a Satanic cult. Social worker Lol Robinson tells Merrily about his client Rowenna, who may be linked to the dead crow—and who has started a friendship with Jane.

Following the fight with her mother, Jane runs away and stays with Rowenna. But when Lol uncovers a shocking truth about Rowenna’s past and Huw learns the history of the church where the crow was found, Merrily begins to fear that her daughter is in great danger from a powerful evil.