AD 670. Pirates attack an Irish merchant ship off Brittany after its crew has surrendered, killing the captain and a prince of Muman. Fidelma and Eadulf survive the assault and reach the Breton coast, where local rivalries and uncertain authority complicate any attempt to identify the attackers.
Because the murdered prince is Fidelma's cousin, the case is both a demand for justice and a potential diplomatic crisis. She follows the pirate vessel's movements through coastal communities and competing Breton factions, discovering that the massacre was not random robbery but part of a plan with political consequences.