The sorcerer Merlin retrieves Excalibur from the Lady of the Lake for Uther Pendragon, who secures a brief alliance with the Duke of Cornwall. Uther's lust for Cornwall's wife Igrayne soon ruins the truce, and Merlin agrees to help Uther seduce Igrayne on the condition that he give Merlin whatever results from his lust. Merlin transforms Uther into Cornwall's likeness with the Charm of Making. Cornwall's daughter Morgana senses her father's mortal injury during his assault on Uther's camp, and while Igrayne is fooled by the disguise and Uther impregnates her, Morgana sees through it, watching Uther as Cornwall dies in battle. Nine months later, Merlin takes Uther's son Arthur. Uther pursues but is mortally wounded by Cornwall's knights. Uther thrusts Excalibur into a stone, crying that "Nobody shall wield Excalibur, but me!", and Merlin proclaims "He who draws the sword from the stone, he shall be king."
Years later, Sir Ector and his sons, Kay and Arthur attend a jousting tournament. Sir Leondegrance wins the chance to try pulling Excalibur from the stone, but he fails. Kay's sword is later stolen, and Arthur pulls Excalibur from the stone while trying to replace the stolen sword. Word spreads, and Merlin announces to the crowd that Arthur is Uther's son and, hence, the rightful ruler. Leondegrance immediately proclaims his support for the new king, but not all are willing to accept. While the others argue, Merlin and Arthur enter the forest, where Merlin tells Arthur that he is the rightful king and that the king and the land are one. Overwhelmed, Arthur falls into a long sleep. When he wakes, Arthur goes to aid Leondegrance, whose castle is under siege by Arthur's enemies, led by Sir Uryens. During the battle, Arthur defeats Uryens and then demands Uryens knight him, handing him Excalibur to do so. Uryens is tempted to kill him but is deeply moved by Arthur's display of faith and decides to knight him (Merlin is stunned, as this is something he did not foresee). Uryens falls to his knees to declare his loyalty, which leads the others to follow suit. Arthur meets Leondegrance's daughter Guinevere soon afterwards and is smitten, but Merlin foresees trouble.
Years later, the undefeated knight Lancelot blocks a bridge and will not move until he is defeated in single combat, seeking a king worthy of his sword. Lancelot defeats Arthur and his knights, so Arthur summons Excalibur's magic and defeats Lancelot, but breaks Excalibur in the process. Arthur is ashamed of abusing the sword's power to serve his own vanity and throws the sword's remains into the lake while admitting his mistake. The Lady of the Lake offers a restored Excalibur to the king, Lancelot is revived and Arthur and his knights unify the land. Arthur creates the Round Table, builds Camelot and marries Guinevere; Lancelot confesses that he has fallen in love with her too. Arthur's half-sister Morgana, a budding sorceress and still bitter towards Arthur, becomes apprenticed to Merlin in hopes of learning the Charm of Making from him.
