Ballet has earned such a reputation for impeccable beauty that director Darren Aronofsky seems to positively revel in dragging it through the gutter a bit. His film "Black Swan" contains all the pretty stuff — the tutus, the immaculate posture, the grace and elegance in movement — that attracts young girls on an almost primal level, but then it delves into what it means to court perfection: the grueling training, the anorexia, the bitchy competitiveness, the repressed insecurity that threatens to come bubbling to the surface.

At first glance, Aronofsky's intentions with "Black Swan" are clear enough: It's an intense psychological thriller that starts off slow and ramps up to some serious gasp-inducing frights. The story involves a professional ballet dancer, Nina (Natalie Portman), who's cast as the lead in a production of "Swan Lake." It's her big break, but the director, Thomas (Vincent Cassel) — a petty tyrant who likes to sleep with his stars — insists she dance two roles: both the innocent princess Odette, who is turned into a swan by a sorcerer; and the sorcerer's daughter, Odile, who impersonates Odette and steals her lover.

Nina is just right for the princess role, a virginal perfectionist who displays a fragile beauty. But she can't please Thomas when dancing as the black swan, Odile — she lacks a certain wildness and passion that the role demands. Enter Lily (Mila Kunis), a West Coast bad girl who effortlessly embodies the sensuality and abandon that Nina cannot. Lily gradually befriends Nina, but Nina can't decide whether she's honest or angling for her role, a paranoia that only increases as Thomas' eyes turn to Lily. He makes her Nina's stage double, the dancer who will take over should, say, an accident happen to Nina.