Those who cringed as James Franco sliced through his forearm in 127 Hours can expect no less harrowing a spectacle from Black Swan, Darren Aronofsky’s unsettling study of a dancer, victimized by her own ambition, unraveling on the eve of her greatest professional triumph.

Is Nina (Natalie Portman) the most versatile talent in the New York ballet company she is to lead in a revival of Tchaikovsky’s Swan Lake? Thomas (Vincent Cassel), the company’s hard-driving taskmaster, isn’t so sure. Her technique is flawless, but where is her passion? Driven to chase perfection with each pirouette and gracefully executed dive, she is also cold, calculating and seemingly incapable of embracing the animal within.

She is ideally suited to playing the White Swan, a heroine pure of spirit, but what about the Black Swan, the wicked impostor who lures a prince to his doom? Thomas thinks Nina lacks the ferocity to master both parts, and he’s right. Frigid, paranoid and so uncomfortable in her own skin that she tears at it until she bleeds, she is a prisoner of her inhibitions and escalating delusions.

Enter Lily (Mila Kunis), a free spirit who never experienced the sort of sheltered upbringing Nina received from her mother (Barbara Hershey), a former dancer determined to keep her forever young, protected from the onset of womanhood. Is Lily a friend? An outlet for Nina’s sexual frustration? Or merely a rival trying to replace her?

Swan keeps us guessing. In Nina’s hallucinatory world, the line between fantasy and reality is blurred to the point of obscurity. Whether Lily is friend, foe or reckless provocateur is every bit as legitimate a question as whether she exists at all. Delicate as ballet might seem, behind the scenes is a psychological minefield. This isn’t grace under fire – it’s burned beyond all recognition.

Perhaps the divide between the worlds of professional wrestling and dance is not so great. Like Randy the Ram, the grizzled protagonist of Aronofsky’s 2008 drama The Wrestler, Nina is a performer addicted to the spotlight, so desperate for acceptance – by both her peers and her audience – that she’s willing to risk her life and her sanity.