Baron Eric von Rothbart, a powerful sorcerer, hunts down women who have betrayed men and transforms them into swans who can only resume their true forms by moonlight. His lonely daughter Odile, who watches the flock and studies spells, longs vainly for his approval. One day von Rothbart tells Odette, the swan princess, that she can break the spell by winning and holding a man's faithful love for one month. He's even chosen a candidate, Prince Siegfried. Unfortunately, the prince is a womanizing hedonist. Should Odette succeed nevertheless, von Rothbart secretly plans a trap for them and the prince's ambitious mother, Queen Clothilde, who schemes to rule in her own right. But he must use Odile, who has befriended Odette and is no longer her father's puppet.