It is the 830s; a time of warring Anglo-Saxon kingdoms, declining monastic standards and outbursts of fear of divine retribution. Elmstow Minster - a community of nuns in the Kingdom of the East Angles - has been recently established to atone for the execution of a young prince. The minster is torn between two camps - pious nuns and those who have no intention of giving up their worldly ways. These ungodly women are supported by powerful, degenerate donors, who treat Elmstow as an aristocratic whoring nest. The abbess of Elmstow has been humiliated by the influence wielded over her minster by these rich patrons and plots revenge. Two naked bodies are discovered, hanged together.
A young, introspective priest, Father Eadred, is sent to Elmstow to spy on the declining standards and against his wishes becomes entangled in the task of uncovering the guilty. He challenges the traditional approach of using an ordeal of hot iron to identify the culprits. Instead, he has the novel idea of exploring the evidence. He faces significant opposition, including an attempt on his life. Eadred is befriended by a hermit monk who becomes the only person with whom he can talk about his detection.
Further murders will take place. As Eadred moves closer to the truth the situation is thrown into further disarray when the minster is attacked by the neighbouring kingdom. Can they be saved and the final culprit revealed?