The King of Northumbria has requested the services of a wise counsel to decide the people's religious future. Among the select priests, elders, and scholars from Ireland and Rome is Sister Fidelma of Kildare. Trained as an advocate of the courts, she was expecting to rule on issues of law. Instead she was plunged into unholy murder.

Dead was the Abbess Étain, a leading Celtic speaker, her throat slashed. With the counsel in an uproar and civil war threatening, the desperate king has turned to the sharp-witted Sister Fidelma for help. With the aide of her dear friend Brother Eadulf and her faith in the truth, she must act in haste before the killer strikes again.