Adelia Aguilar, King Henry II's mistress of the art of death, is commanded by the king to accompany his ten-year-old daughter Joanna to Palermo to marry William II of Sicily, and she takes along her Arab companion Mansur, her lover Rowley, and the Irish sea captain O'Donnell, all of whom come in handy when members of the princess's household come under attack by a murderer.
