AD 664. On her journey home from Rome, Fidelma stops at Genua after learning that her former teacher Brother Ruadán is dying at the abbey of Bobium. The monastery lies in a region divided by warfare and religious hostility, and Ruadán's final words direct her towards a danger he could not investigate himself.
Alone and far from Irish legal authority, Fidelma enters a conflict involving local rulers, rival Christian factions and communities still attached to older gods. A sequence of murders reveals a conspiracy capable of provoking civil war, forcing her to rely on argument and observation where her formal status offers little protection.