Don't know what it is about films like this one. They drain you completely while making you wonder about the pointlessness of perfection.
Black Swan is about ballerina Nina Sayer (Portman) who lands the role of the Swan Queen in a production of the Tchaikovsky classic. Normally, this should have been a happy occasion but with a mother who pushes her all the time, she strives to get picked in lead roles only to see roles go to lesser talents. Years of failure to get that big break, including an overwhelming sense of paranoia make her a tad psychotic, easily given to hallucinations and such. When she does get the role, she finds herself even more insecure than before. The director Thomas Leroy (Cassel) doesn't help matters by constantly riling her for being too frigid instead of losing herself in the character.
For the highly disciplined Nina, however, giving up control is an alien concept and she can't stop striving for perfection. Her psychosis is further heightened when she tries (initially, unsuccessfully) to be play both Odette (the white swan) and Odile (the black swan and evil twin) from the story. Enter Lily (Kunis), a free spirit and a natural dancer who makes her lose inhibition. After a night of clubbing, there is a slight tension between the two but they get past it. However, it is when the hallucinations grow stronger and seemingly real that the trouble starts. Nina's mother (Barbara Hershey) calls up the ballet company to tell them she will be backing out. Nina reaches the venue in time to convince them otherwise, determined to play the role. Does she give the performance of a lifetime or does she succumb to her insecurities? Well, that's what the rest of the film is about.
What is brilliant about the film is that while Swan Lake plays out on stage during the climax, it also is playing out in the lives of the characters playing those parts. Almost like life imitating art imitating life....