After the fall of Camelot at the Battle of Camlann, Lin, daughter of King Arthur and Queen Gwenhwyfar, is torn by grief and self-doubt.

Twelve years later, while exploring the deserted castle with her four children, Lin tells them about her own childhood in the distant kingdom of Orkney, before she learned the truth of her birth.

At five years old, the only mother she knows dies, leaving Lin alone with Dafydd, the boy she believes is her true elder brother.

On Lin's twelfth birthday, she is given a slave collar and a new master: Prince Mordred, who knows she, not he, is the true heir to the throne of Camelot.

Kay notices her family resemblance and takes Lin to Arthur, who wants to avenge his innocent daughter for the abuse she endured.