"King Uther has died. Both Arthur and Mordred (here Mordred is the lover of Arthur's sister Morgan) want to be his successor. Mordred has tyranny in mind, Arthur intends to be a king for the people and has Merlin on his side, who is his counsellor rather than a magician. Arthur draws Excalibur from the stone, but Mordred refuses to give in.
Lancelot, the son of the French king Ban of Benwick, is looking for king Arthur, the only lord he wants to serve. In a forest he meets the young lady Elaine. When he is ambushed (by Mordred's men who are waiting for Arthur) a knight comes to his aid. Lancelot does not like to be helped and challenges the knight. After a long and undecided duel the knight turns out to be Arthur. Lancelot offers him his service, and so does young Perceval, who comes to pick up his sister Elaine.
Lancelot joins Arthur on his way to the council at the ring of stones (Stonehenge). There Mordred tries to kill Arthur, but Lancelot saves him. The war is on. After his victory Arthur establishes the Round Table. But soon after he gets into conflict with Lancelot, who does not want him to pardon Mordred and Morgan.
Guinevere is to marry Arthur, but on the way to Camelot she is captured by an evil knight. It is Lancelot (as a nameless knight) who saves her and orders the evil knight (who will be one of his companions later on) to bring her to Camelot in safety. After the wedding the knights are to pay homage to their king and queen. Lancelot reappears and is the first to kneel before them. Arthur makes him the champion of the queen.
Lancelot and Guinevere feel deeply for each other, but do not consume their passion. Instead Lancelot marries Elaine to silence the gossip about him and the queen, and he takes his bride away from the court. Gawain and Gareth are Lancelot's loyal companions: Gawain watches over Elaine, while Lancelot and Gareth are out fighting the Picts. Perceval visits them and talks about his quest for the Holy Grail. Elaine dies after giving birth to a son: Galahad.
Mordred and Morgan are responsible for the death of Merlin and a plot to get Lancelot back to Camelot and Guinevere. Lancelot pretends to have lost his feelings for her and flirts openly with lady Vivien. The queen is hurt by this and visits his chambers late at night. When Mordred's men (amongst them Agravaine) are banging on the door and all is lost, she sees proof of Lancelot's love for her. They kiss for the first and last time, right before Lancelot kills Agravaine and his men and brings the queen to safety.
King Arthur has to judge his best friend and wife, but does not give in to Mordred's demand to have them killed. Instead Lancelot is banished to France and Guinevere has to retreat in a convent. The union of the Round Table falls apart and Mordred finds support to challenge Arthur again.
Once again the civil war rages over the country and Arthur is mortally wounded. It is Lancelot who throws Excalibur into the lake and then kills Mordred. Afterwards Lancelot and Perceval enter the ruins of Camelot. Perceval has a vision of the Holy Grail and hears a heavenly voice that tells him Lancelot will be forgiven for his sins and Lancelot's son, Galahad, will be the most accomplished knight ever."