In AD 670, Fidelma accompanies an Irish delegation to a church council in the Frankish lands, where Celtic representatives face hostility over doctrine and discipline. A senior churchman is murdered and a valuable reliquary disappears, threatening to discredit the visitors and intensify disputes already dividing the council.
Fidelma's inquiry enters an abbey marked by factional rivalry, exploitation and abuse concealed behind ecclesiastical authority. Working in an unfamiliar legal environment, she must uncover the relationship between the stolen relic, the dead delegate and those who use religious reform to protect private crimes.