King Arthur's engagement to Princess Mithian presents him something he's never faced before - a perfect match.

As Morgana's forces capture Camelot, Arthur at last comes to see his uncle's treachery. He is reluctant to flee, but Merlin bewitches him into escaping with him, temporarily blocking his memory and dressing him as a peasant. Elyan, Gaius, and Gwaine are taken prisoner, though Morgana is impressed by Gwaine's performance in trials by combat. Separated from Leon and Percival, Merlin and Arthur fall in with smugglers Tristan and Isolde, during which Merlin's spell wears off and the young king can reveal his identity to them. The quartet escapes to Ealdor, Merlin's village, where a wounded Arthur is nursed by Guinevere as Agravaine and his army close in.

Merlin summons the dragon to vanquish the pursuers and uses his magic to kill Agravaine. Hiding in the woods with Guinevere, Tristan and Isolde, Arthur confesses his self-doubt to Merlin and feels he has failed his subjects, but Merlin proves to him that he is worthy to be king by getting him to extract the legendary sword from its stone. In front of Leon and Percival and many other fugitives from the court, Arthur accomplishes the feat, inspiring them to claim back Camelot by entering through the same siege tunnels and freeing the prisoners. Finally, Camelot will be reclaimed after magic and sacrifice, and Guinevere will be proclaimed its queen.