Ballet is more than a profession or even an art form; it is a calling, almost a cult, that demands the ultimate commitment. Ballerinas give everything they have. Director Darren Aronofsky, always drawn to stories about obsession, now takes us inside the mind of a woman who is becoming unraveled.

Ballet is about art but also about discipline and control. It tests every muscle in the body and every bit of resolve of the spirit. Natalie Portman plays Nina (the very name evoking a sort of uncertain syllabic wobble), the daughter of a failed ballet dancer (Barbara Hershey) who has focused on Nina as her second chance to realize her dreams of stardom. Nina is a child-like adult, completely sheltered by her mother and her nun-like commitment to dance.

She wants more than anything to have the lead role in that most revered of ballets, Swan Lake. It is really two lead roles — the story is about a princess who is turned into a white swan. Her chance for breaking the enchantment is lost when the prince is seduced by her nemesis, the black swan. The director (a faun-like Vincent Cassel) tells her he is certain she can perform the part of the white swan with technical perfection. But he is not sure she has the passion, the sensuousness, the willingness to take risks to play the black swan. As she struggles to both maintain and lose control, the world around her distorts. Her mother’s art studio is filled with dozens of portraits of Nina, and their eyes move as she walks by. Nina keeps catching glimpses of herself in mirrors and reflective surfaces. The company’s newest dancer is Lily (Mila Kunis), her name another wobble on the tongue. Is she a friend, a rival, to be feared, hated, desired, overcome? Is she just another of Nina’s reflections?

Visual and narrative symbols of duality and doppelgangers are everywhere, with black, white, gray, and toe shoe pink as the movie’s palette. The script is heavy-handed at times, especially in the scenes with Nina’s mother. But Aronofsky draws us into Nina’s struggles with reality until, like her, we are never sure whether we can trust our eyes. Portman, who studied ballet for a year and did most of the dance moves herself, is superb her struggle to stay in control showing in every muscle, her yearning to break free fighting with her need for approval. Cassel’s louche manipulator, Kunis’ confident rival, and Winona Ryder’s brittle rage as the fading prima ballerina whose role (and lipstick) Nina covets are all exceptional and like Nina herself we experience the performance of the ballet itself as both tragedy and triumph.