Atonement of blood - Peter Tremayne

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? It is a female name?
Who is behind the assassination attempt? Colg's lawyer sister, Fidelma of Cashel, and her companion, Brother Eadulf are charged with solving the mystery. They must journey into the territory of their arch-enemies, the U Fidgente, uncover the evil secrets in the dark, brooding Abbey of Mungairit, and venture into the threatening mountain fastness ruled by a godless tyrant. Danger and violence are their constant companions until the final devastating revelation...