Guests arrive at the palace for a costume ball. Siegfried's mother commands him to dance with six princesses and choose one as a bride. Siegfried complains that he does not love any of them. Von Rothbart arrives in disguise with his daughter Odile. He has transformed Odile so that she appears identical to Odette in all respects except that she wears black rather than white. The prince mistakes her for Odette and dances with her. Odette appears as a vision and vainly tries to warn Siegfried that he is being deceived. But Siegfried remains oblivious and proclaims to the court that he intends to make Odile his wife. Von Rothbart shows Siegfried a magical vision of Odette and he realizes his mistake. Grief-stricken, Siegfried hurries back to the lake.