Ireland, AD 671. King Colgú's chief bishop and trusted adviser is murdered in a fortress held by the formerly rebellious Uí Fidgente. The commander of the king's bodyguard is accused and condemned under a new legal procedure, and his execution threatens to reopen conflict between the rival peoples.
Fidelma travels into hostile territory to challenge evidence that appears overwhelming. She must investigate the bishop's mission, the fortress hierarchy and the political purpose served by a rapid conviction, while preventing personal vengeance and legal innovation from producing another war.