This article includes spoilers.
The movie Black Swan starring Natalie Portman is a psychological thriller based on the story of the ballet Swan Lake, first performed on the stage of Moscow's Bolshoi Theatre in 1877. The ballet Swan Lake is the story of a princess named Odette who is turned into a swan by an evil sorcerer. She must fall in love to a man who will be faithful to her in order to break the spell.
The movie Black Swan uses characters in ways that are similar to their ballet counterparts. Yet, in some areas the similarities diverge. Among other differences, the movie takes the theme of deception, delusion, and mistaken identity to new heights, morphing characters of the ballet into one another.
In the ballet, Odette who lives under the spell of the evil sorcerer von Rothbart appears as a woman at night. During the day, she is magically transformed into a swan and forced to live by a lake filled with the tears of her grieving mother. Odette is beautiful, innocent, fearful, and also na?ve.
Nina of the movie Black Swan is Odette. She is terrified of making mistakes, of not appearing to be "perfect" in the eyes of the ballet company director Thomas Leroy. Her naivety and unhealthy desire for approval allows her to be manipulated by the director, who incidentally, exhibits traits from the actual ballet of both Prince Siegfried and the sorcerer.
Prince Siegfried and von Rothbart
In Nina's mind at the outset of the movie, the director Leroy is the good Prince Siegried. She believes that he loves her, forsaking all others. Like the ballet's Siegfied, Leroy promises to make Nina his 'Queen', the lead in the production.
Interestingly, in the American Ballet Theatre's version of Swan Lake, von Rothbart appears early in the production as a young and handsome man luring Odette into the spell. Later, he is revealed as a repulsive, bird-like creature, his true evil self.
As the movie Black Swan progresses, Nina begins to believe that Leroy's true persona is the evil sorcerer.
Odile, von Rothbart's daughter, who resembles Odette
In the ballet, one person dances the roles of both Odette and Odile. Odile is disguised as Odette to trick Prince Siegfried into being unfaithful. Odette and Odile resemble each other except that Odile wears black rather than white.
In the movie, Nina sees rival dancer Lily as Odile. They look alike. Even their companions at the nightclub ask if they are sisters. They dance the same roles. But Lily is free-spirited and dangerous, much like Odile.
Nina fears that Lily is trying to steal her position as Swan Queen, that the director will be duped by Lily's deceptions.
Odette becomes Odile
In the ballet, once the Prince declares his love for the wrong girl, Odette, a victim of deception, is consigned to remain a swan forever. Death is her only escape.
In the climax of the movie, Nina meets her end, and as Odette once again, declares that she is perfect.
Some versions of the actual ballet portray also Siegfried dying with Odette. Others portray him living alone with the pain of losing her.