An untimely death leads Merlin to locate Arthur and urge him to come back to Britain; chaos ensues when Gundleus assaults Avalon.

Arthur takes Gundleus prisoner. Nimue struggles with the trauma of her rape and plans to kill Gundleus. Arthur learns that Gundleus' uncle Gorfydd is preparing for war. Nimue tries to pull Derfel into her plans, but Derfel can't betray Arthur.

Nimue returns to Avalon, where she is found by Merlin. Derfel and Owain travel to collect taxes from King Cadwys. Gundleus returns to Caer Cadarn.

Arthur and the tribe kings enter peace talks. Arthur meets Guinevere, Ceinwyn's lady-in-waiting, while traveling.

Arthur and Guinevere meet secretly before Arthur and Ceinwyn are to be married.

Arthur believes that Bedwin will be able to negotiate peace with Gorfydd; however, when Morgan and Derfel arrive in Powys, they discover a horrific site.

Gorfydd allies with the Saxons and declares war; Arthur admits he exiled Nimue to the Isle of the Dead.