The story follows Nina (Natalie Portman), a ballet dancer at a prestigious dance company in New York, who is given the opportunity to play the two swans, the White and the Black, in a Swan Lake production. Though the director (Vincent Cassel) is not entirely certain of her abilities to act as the Black Swan, he attempts to make her confront her sexuality and inner darkness in order to make her convincing for her role as a seductive sorceress. Nina's fragile state of mind, along with her inexperience of the outside world due to her overbearing mother (Barbara Hershey) lead her to question reality. To top all that, her relationship with her replacement/rival (Mila Kunis) and her self-destructive predecessor (Winona Ryder) lead her on the verge of sanity - and a physical (?) transformation.
All the performers excel under Aronofsky's sure hand; Natalie Portman, a young though heavily experienced actress, plays perhaps the role of her life as Nina. Throughout the film, the camera is always centered on her and the script gives her a variety of opportunities to emote and dance onscreen in surprisingly different ways. Mila Kunis, who hasn't really proved her worth before gives perhaps her first solid performance as the very personification of the Black Swan (while Nina originally starts off as the embodiment of the White one). Ryder's role is very limited but she's perfectly suited for that (in an inspired casting decision that's reminiscent of Rourke's in Wrestler). Hershey's role is perhaps the most thankless, as Nina's mother is written as a just-more-subtle version of Norman Bates' mother in Psycho, but she gives her best to make her look credible. Clint Mansell's score consists of dark variations on Thaikovsky's Swan Lake motifs, although he could do something more given the existing material. But nitpicking aside: 9/10