Winter, 670 AD. King Colg has invited the leading nobles and chieftains of his kingdom to a feast day. The gathering is interrupted by a religieux claiming that he has an important message for the King. Suddenly, the man, shouting "Remember Liamuin!" stabs King Colg. The assassin is slain but Colg is on the verge of death. Who is Liamuin? Colg's lawyer sister, Fidelma of Cashel, and her companion, Brother Eadulf are charged with solving the mystery.