In the mid-7th Century AD, the Venerable Dac n, a much respected and beloved scholar of the Celtic Church, has been found murdered while on a visit to a remote abbey in the Irish Kingdom of Muman. When Dac n's foul death is used by a neighbouring kingdom to demand reparation from Muman, bloody war seems imminent.

Summoned by Muman's dying king to investigate, Sister Fidelma is asked to solve the mystery of the brutal killing and by doing so to prevent the inevitable war breaking out between the two opposing kingdoms. She sets out for the remote abbey with a warrior named Cass - and very little time. But there are more sinister forces at work behind Dac n's death than just political intrigue...