The book's protagonist is Morgaine, priestess of Avalon, who is King Arthur's half-sister. Their mother Igraine is married to Uther Pendragon after Morgaine's biological father, Gorlois, is killed in battle. Rumors spread in Avalon that before Igraine knew her husband Gorlois was killed, Uther consulted with the Merlin, who used his magic to transform the king into the likeness of Gorlois and thus gain access to Igraine at Tintagel. He spent the night with her and they conceived a son, Arthur. Morgaine witnesses Uther Pendragon's accession to the throne of Caerleon after his predecessor, Ambrosius, dies of old age. Uther becomes her step-father, and he and Igraine have a son, Arthur, Morgaine's half-brother.