By now we know that the words “A Darren Aronofsky Film” promise us a fever dream, an intense psychological thriller, a discomforting but enthralling experience.

We also know that we’re likely to see very good actors deliver performances so maniacal that veins will bulge and pulse across their temples and throats, as if they’re androids plugged into more voltage than they can survive. And we’ll be confounded by surreal visions  — a man digging through the flesh of his own head, Ellen Burstyn fighting a haunted refrigerator, Hugh Jackman transforming into a tree, or the magnificent ruin of Mickey Rourke’s face.

And we’ll see characters who go to extremes to get what they want, even if it ruins them in the end. But oh, the glory of that ruin.

Black Swan — Aronofsky’s new film about an uptight, obsessive ballet dancer who is determined to score the leading role in “Swan Lake” — is definitely a rush. Aronofsky fans will get what they expect.

As the young and tormented Nina, Natalie Portman makes a riveting show of dedication and desperation on the dance floor. Nina is possessed by an almost demonic drive to become and eclipse Beth, the dance company’s famous starlet, played with frightening conviction by Winona Ryder. To achieve her ambitions, Nina will have to impress a tough and exploitative director (Vincent Cassel), which may require some private performances in his penthouse apartment. She’ll have to cope with her mercurial and manipulative mother (Barbara Hershey), who fuels Nina’s selfish ambitions even as she snarls with vicious jealousy.

It’s the most demanding performance of Portman’s career, and she hits all of her marks perfectly.

But the script doesn’t give her what could have made a good performance great. Her lines, like those of the Wicked Director, the Fearsome Mother, and the Snippy Girls all around her, sound like placeholders for the real dialogue… which they must have run out of time or money to compose. The Wrestler, whether you enjoyed it or not (I didn’t), was at least a movie about characters — detailed characters with distinct personalities, time-worn voices, people who seemed to be living on the other side of town. Black Swan, by contrast, lacks lifelike human beings. Instead, it gives us simple outlines of characters. It has archetypes. Primal forces. Mythic figures.

And that should be fine. You might just say “It’s a fairy tale. These figures are simplistic for a reason.” The story of Black Swan adheres closely to the beloved myth of “Swan Lake.” These are supposed to be exaggerated characters, big as Greek gods, titans clashing in a storm of power and emotion. That’s certainly the picture that Tchaikovsky’s sonorous music paints, and Aronofsky wants to live up to that.

Moreover, we’re viewing the world through Nina’s warped psyche. Her attention is so narrowly focused on inheriting Beth’s crown that she’s made herself a nervous wreck. Everyone around her is either an advantage or an obstacle, someone to seduce or to shove out of the way. She’s wound herself so tight in the cords of her own ambition that her skin is splitting open.

And insofar as Black Swan brings the myth to life through dance, it is an exhilarating success — that is, if you find a story of innocence lost in a bloody calamity exhilarating. With the impressive camerawork of Matthew Libatique (as usual), Aronofsky draws us into the dance until we’re breathless with the fluid motion of the dancers, the whirling lights. Hurricane-force waves of music crash from the movie into the audience until we’re either dizzy with the thrill or seasick from the chaos.

The colors and textures of the elaborate costumes — costumes that morph into frightful new forms as dark forces take hold of Nina’s imagination — are a fantastic spectacle. And when the black-feathered phantom of the title is fully unveiled, striking a triumphant pose mid-stage, well… what can we do but surrender? Aronofsky is one of the few American directors capable of painting indelible images, and that’s one for the ages.

These strengths do make Black Swan quite a memorable experience, and one I wish I could recommend without Capital “D” Disclaimers.

But I cannot.

Aronofsky’s weakness is that, in his roaring confidence, he lets his giddy enthusiasm for intensity get the better of him, and he fails to give enough attention to story.

What little suspension of disbelief I could sustain through the film’s first half was disrupted by three things.

First: The mockery of Beth as a has-been seems specifically designed to make us think of Winona Ryder herself, and how she once held a Portman-like place on the big screen. That set off a wave of laughter in the audience, making it clear that we were all thinking about the stars instead of the characters.

Second: The film takes an unfortunate turn down Mulholland Drive. As Nina feels threatened by a newcomer, a graceful dancer named Lily (Mila Kunis), she becomes obsessed with out-performing her. The two actresses are evenly matched in their commanding screen presence. But they’re both so attractive that the director gives in to the temptation for some soft-core girl-on-girl action.

“Oh, but that’s about Nina’s self-worship, her desire to turn a girl who might be a threat into someone who will serve her completely.”

Yeah, yeah. Sure. There are a dozen ways to explain why the movie contrives sex scenes between the two. I’m not objecting out of any prudish aversion to sex scenes. But this particular twist has been done too many times before — most notably in films like Bound and Mulholland Drive — and it leaves a stain on the movie that lingers as its most talked-about flourish. Instead of enhancing the viewer’s imaginative involvement, it becomes The Scene that everyone will talk about, The Scene that might break the Internet, The Scene that distracts us from characters and makes us suddenly very aware of The Actresses. Few moviegoers are likely to remain focused on Lily and Nina during this tangent; instead they’ll be thinking, “OMG, Natalie Portman and Mila Kunis are both smoking hot and really going for it.”

But that’s not the biggest disruption. The movie’s most arresting presence is also what spoils the mythic splendor. And I’m not talking about Natalie Portman. Sure, she’ll win her Oscar. And deservedly so, for committing so completely to such a tormented character. But no, Nina is not the heart of the movie.

This movie belongs to Mila Kunis.

Kunis, dazzling those of us who thought she brought a spark of genius to the sitcom That 70’s Show, proves to be a far more formidable big-screen presence than even her admirers would have guessed. She dances effortlessly into the film and steals it right out from under Portman. She makes Lily a living, breathing, dangerous human being, seeming capable of warmth, compassion, and humor, even as we suspect (with Nina) that she’s plotting a betrayal behind the scenes. “Look!” Aronofsky practically shouts from off-camera. “Don’t you see how capable she is of being both the White Swan and the Black?

Next to Lily, Nina seems all the more pathetic and ridiculous. And there’s the problem. Even though Kunis is voicing the same trite, predictable, on-the-nose dialogue that all the other actors barely manage to recite without embarrassment, she brings us into the “real world,” the world in which The Wrestler took place, a far different world than the wicked wonderland of Nina’s psyche. Around her, everyone else looks like a bunch of soap opera characters.

Thus, when the film pulled away from its most interesting character and headed into its apocalyptic dénouement, I started checking my watch. Aronofsky seemed to run out of storytelling ideas, piling on the horror-movie jolts and laughably flamboyant spectacles of Nina’s fractured psyche. Nina’s madness sweeps us up and carries us away, far from the land of storytelling, and drowning us in a current of melodrama. (Or is it meant to be comedy?) Its most striking images, including a slow-turning music-box ballerina figure that recalls Inception‘s spinning top, end up seeming like light, sound, and fury signifying nothing at all or whatever you want them to be.

I never really cared about Nina. I haven’t been enchanted into elevating Portman to “goddess” status as so many have. To me, Nina seems like a petulant, whining, bitching overachiever, like certain girls I encountered in high school whose vain, competitive, backstabbing behavior made me eager to escape their company. Villainous though Lily might be, I wanted to follow her character and leave the rest — including Nina — to implode in their own self-absorption.

Is there anything more to take from a story like this than the obvious conclusion that self-destructive behavior can lead to, yes, self-destruction?

Myths like “Swan Lake” can serve as warnings. They question the widespread American ethic of “Just Do It” — follow your passion, no matter the cost. If we pursue all of our dreams and pay any price, but have not love, we are just clashing cymbals. Black Swan could have been that sort of cautionary tale.

But I don’t think it is. If it’s a cautionary tale, why does it feel so triumphant and celebratory in the end? “Look at Nina,” Aronofsky is singing. “Isn’t her misery grand? Isn’t this disintegration glorious?” The film seems to suggest that it’s better to rise above by embracing both the light and the dark side, even if it means you burn out like a supernova.

Aronofsky’s last two films have changed my mind about the movie that announced his arrival — Requiem for a Dream. Many people thought it was too over-the-top. I was among those who defended it as a “cautionary tale,” saying that the wild intensity of its drug sequences and violent stretches were there to represent the dangerous power of addiction.

But now I feel differently. I think Aronofsky has the talents of a great artist, but he’s also an adrenalin junkie, and that keeps his films short of greatness. When, in the end credits, he splashes “Directed by Darren Aronofsky” and “A Film by Darren Aronosfky” across the screen, as if wanting to make sure we get the point, well… the point has been made. He aims to impress. And in his eagerness, he goes for violent energy over poetry, shock over suggestion, emotion over intelligence.

If and when that ever changes, he’ll become a powerful director indeed.