During a hunt, Siegfried sees a beautiful white swan adorned with a crown. Magically she transforms into a woman before his eyes. She is Odette, the Swan Queen. Odette explains to Siegfried that she and other maidens like her are under the spell of Von Rothbart, an evil sorcerer. Under his wicked enchantment, she may only return to her original human form for the brief time between midnight and dawn. To break the spell, a man must swear his eternal love to her. Struck by this confession, Siegfried promises to rescue Odette with a pledge of love. Odette replies that this is impossible but Siegfried declares that he will not marry another and that he will release her from the spell with his pledge. As dawn breaks, the lovely apparition fades away.
At Siegfried’s home the next evening a birthday party is being held in his honor. His friends amuse him with dances from around the world. Suddenly a mysterious creature appears. He believes her to be Odette but she is Von Rothbart’s daughter Odile, whom her father has transformed into Odette’s likeness. Siegfried, blinded by love, mistakenly asks for Odile’s hand in marriage. The spell is broken and Von Rothbart triumphs.
Siegfried runs to the lake to find Odette. He finds her weeping for her lost love. Consumed with remorse, Siegfried begs her to forgive him but it is too late. Von Rothbart removes Odette from his embrace forever.