After King Arthur hears of the crimes of King Royns of North Wales, he calls the knights from all his lands to a general council at Camelot. When the council is assembled, there comes a damsel sent by the Lady Lyle of Avilon. Under her mantle, the damsel has a sword which is fixed in its scabbard and cannot be drawn out except by a knight completely pure of heart. It is her curse that she must wear the cumbersome sword and scabbard everywhere she goes. Arthur and all his knights try to draw the sword and fail. At last, a prisoner among them, Sir Balyn, newly released from the dungeon and shabbily dressed, asks that he be allowed to try, for though he has been accused of a crime, and though his apparel is humble, he believes himself worthy. He draws the sword out easily, making some of the other knights fiercely jealous, and he says he will keep it, even though it is a fated sword: it will murder his dearest friend. Arthur apologizes for misjudging and mistreating Balyn, a man proved so noble.
Balyn accepts the apology and prepares to leave the court. Before he has left, the Lady of the Lake arrives and demands the gift Arthur promised her when she gave him his sword. She wants either Sir Balyn's head or that of the damsel who gave him his sword. Arthur refuses, and Balyn, recognizing her as his mother's murderer, hacks off her head. Arthur is outraged as a visitor to the court she was in his safekeeping and says he will never forgive Balyn for this murder. Balyn leaves and resolves to kill the tyrant King Royns and thus win back Arthur's respect. Sir Launceor of Ireland, one of Arthur's knights whom Balyn's success has humiliated, asks permission to ride after Balyn and avenge the Lady of the Lake; Arthur, still angry, grants it.
