Father Brown (Mark Williams) visits a women's prison to hear confession from Katharine (Kate O'Flynn) a woman waiting to be hanged for the murder of her husband. Under the seal of the confessional she tells him that she's arranged the death of her former lover, Raymond (Benjamin Fisher). Was that terribly naughty of her? Father Brown visits Raymond only to be startled by a gunshot - revealed to be Raymond scaring away an eagle. Raymond is packing up to leave Kembleford and entrusts Father Brown with a revolver inside a wooden box. His feelings of shame about Katharine give him dark thoughts and he doesn't trust himself with it. Father Brown crosses paths with Inspector Mallory (Jack Deam), on his way to investigate the gunshot, who observes the gun box. When the Inspector finds Raymond's body with a bullet wound to the head, he only has one suspect in mind...