Black Swan is a finely-made, multi-layered, genre-straddling smash with a few minor flaws in its finish. Centered on a stunning, controlled performance from Natalie Portman, the film is a character study, a performance documentary, an allegory, and also a credible horror movie.

Portman utterly inhabits Nina Sayers, a ballerina in her prime who is still very much a little girl. She unflinchingly bows to the pressures of her mother and her director while widely skirting the objects of her obsession – including a unstable prima ballerina and a transgressive new soloist, Lily.

Mila Kunis as Lily is magnetic, tearing through relatively few scenes with offhand sexuality that further amplifies the tour de force from Portman. Also, it must be said that the score and sound design is virtually a third lead character. Quotes of Tchaikovsky are set off by electronic throbs, and Nina’s movements are often accompanied by an unsettling fluttering of feathers.

While the movie is unquestionably strong, the dissonance between its competing genres renders the final product slightly unsatisfying. The character study of Nina is never entirely fulfilled as the movie transitions to sheer performance and terror. The allegory paints many of the secondary characters as simplistic cliches who never seem credible in the wake of Portman and Kunis. Barbara Hershey, in particular, seems clownish by comparison. Even as the movie turns into a literal ballet, the performance documentary aspect seems to fizzle, with relatively little actual dance as payoff to the attention paid to Portman’s preparation (though, what we do see of the ballet is as visceral as it is visually sumptuous).

All three of those genre labels could also be assigned to Aronofsky’s prior film, The Wrestler, a similarly flawed movie framed around a standout performance. However, Black Swan benefits from the addition of horror, because it’s the scary movie that wins out. After subtle background teases, the terror bares its teeth in a sequence of events that plays out like a sickening fever-dream.

It’s those frightening thrills that see the movie through to its resolution, even as threads dangle from the character piece, the allegory, and the performance. Thanks to the horror, the dangling is good dangling – talked about in the car on the way home loose ends, not the untread paths of an incomplete film.

These minor flaws – mere chinks – mount to prevent Black Swan from becoming a more grand, sweeping movie. Aronofsky is as much a part of the problem as he is the orchestrator of success. Too often he errs too gritty and too handheld, staying in the style of The Wrestler when Swan begged for the painterly beauty of The Fountain. And, though Portman and Kunis shine, the flatness of the supporting cast is only excusable if the film is read as purely allegorical. Winona Ryder, in particular, is wasted – all along it feels like we’ve missed a crucial scene with her.

The result is still thrilling, and still awards-caliber in direction, cinematography, and Natalie Portman’s performance. However, even as Aronofsky exerts yet more control over his end product, it falls just short of being a modern day classic on the order of Requiem for a Dream, and even the oft-maligned The Fountain.