The infant Mordred and his mother are brought to Merlin's hall at Ynys Wydryn, where she and the child are placed under the care of Merlin's priestesses, Morgan (Arthur's sister) and Nimue (Merlin's lover). Merlin himself has not been seen in Britain for many months. The narrator, Derfel, is a young foundling at Ynys Wydryn who had been adopted by Merlin. Born of a Saxon woman named Erce, Derfel and his mother were once captured in a raid by Britons and enslaved. Their British captors were later raided in turn by Gundleus, King of Siluria, and his druid Tanaburs. Derfel was to be one of the sacrifices to the gods as a tribute from the victorious raiders, but survived being thrown into the "death-pit" and is henceforth considered by Merlin to be favoured by the gods. Having survived the failed sacrifice, he is also entitled to take the life of Tanaburs. Derfel is in love with Nimue, who binds him to her by scarring both of their hands and making Derfel swear that he must always obey her.