When Mara attends the Feast of the Holy Cross at Kilnaboy Church, it is just another duty in her busy life as Brehon of the Burren, responsible for upholding the kingdom's ancient laws. But this special day has drawn the faithful of Ireland and pilgrims from across Europe, for Kilnaboy Church holds a prized relic-a piece of the true cross-inside its tower. When the tower catches fire and the relic is destroyed, chaos breaks out, and Mara begins her investigation. But before she can round up the many suspects among the frantic crowd-including a follower of Martin Luther, who despises such relics as false idols-another crime is committed. A naked body is found dead, spread-eagled in the shape of a cross, in the graveyard behind the church. Sensing a connection between the crimes, it is Mara's task, along with her law-school pupils, to find the guilty parties and uphold the power of the law.