Swan Lake begins in the forest. Prince Siegfried in hunting and he sees a beautiful swan. As he is aiming his bow, she turns into a woman named Odette. She explains to him that she is a princess turned to a swan by an evil sorcerer. During the day, she is a swan, and must swim in the lake of tears, and during the night, she may be a woman again.
The spell can only be broken if a prince promises to love her forever. She tell Siegfried that if he refuses her, she will be a swan forever. Luckily, he falls madly in love with Odette.
But at the ball, the evil sorcerer put a spell on a woman named Odile, to make her look exactly like Odette to Prince Siegfried. He proposes to her, and Odette is heartbroken. She tries to kill herself and throws herself in the lake. Siegfried realizes what he has done and throws himself in the lake with Odette.
In the finale, the two are transformed to lovers in the afterlife.