With Arthur's forces outnumbered Merlin arrives in his guise as the aged sorcerer to defeat Morgana's army with magic. Arthur kills Mordred but is wounded and rescued by Merlin, who reveals that he is a wizard. Arthur is initially hostile but, advised by Gaius, allows Merlin to take him to the healing lake of Avalon. On the journey Arthur comes to appreciate everything Merlin has ever done for him and eyes him with a new respect, even softening in his attitude to magic. But Morgana is pursuing them. Can they make it to Avalon ahead of her?