In the 5th century, King Arthur, misunderstood by his knights and faced with peasant revolts, sees the Lady of the Lake intervene to revive his faith. Léodagan and Séli of Carmélide plot to marry their daughter Guenièvre to Arthur and place Yvain at the Round Table. Lancelot, in love with Guenièvre, distances himself, while the quest for the Grail stalls.