The dove of death

AD 670. An Irish merchant ship is attacked by pirates off the Breton peninsula. The captain and one of the passengers, a prince from the kingdom of Mumam, are killed in cold blood after they have surrendered.
Among those who manage to escape death are Sister Fidelma and her faithful companion, Brother Eadulf. Safely ashore, a grim task confronts them. The prince was Fidelma's cousin and she vows to bring his killers to justice. But her only clue is that the attacking ship was carrying the symbol of a dove.
The quest for retribution will be the most dangerous the pair have undertaken. leading Fidelma to the brooding fortress of Enez Lovr, and Koulm ar Maro - the Dove of Death