The catchiest tagline right now for BLACK SWAN, director Darren Aronofsky’s follow up to THE WRESTLER, is “psychosexual thriller.” It might also billed as an action flick, what with all of Natalie Portman’s jumps, twirls, plies, her mad dashes down hallways and corridors, her rampant mirror smashing, her feverish dancing in a sweaty, crowded nightclub and her boisterous “lezzy fantasy.” Shot handheld, much of it from Portman’s point of view, it makes for a frantic, seat-gripping hour and a half.

Portman plays Nina, a dedicated young dancer obsessed with all things ballet. Raised by an equally obsessive mother (Barbara Hershey), Nina’s innocent childhood dreams of becoming a prima ballerina have only intensified with age. She’s coddled and babied, dressed, undressed, put to sleep and woken up by her fanatically doting mom. Like Randy (Mickey Rourke) in THE WRESTLER, Nina will stop at nothing to be the best, driving her body to its limit with an unforgiving diet and training regimen. Where the two differ, of course, is Randy has a life outside of his profession, whereas Nina does nothing, absolutely nothing, but practice and perform.

Now that she’s landed the lead in her company’s next show, “Swan Lake,” all her undivided mental focus is starting to get the best of her. You get the sense that with a life like hers, Nina was always a little off – quiet, shy, socially awkward – but the mounting pressure of a role all her years of practice have failed to prepare her for is causing new problems. She hears things, sees things, imagines people who aren’t there, enacts conversations she isn’t really having, and bleeds mysteriously from her fingers and back. She’s paranoid, competitive and jealous, and she projects all these insecurities on Lily (Mila Kunis), a free-spirited, fun-loving dancer new to the company. Lily is probably just a nice, friendly girl, but Nina is convinced that she’s out to ruin her. As the audience we see things from only Nina’s perspective and so we’re not sure who to believe.

The suspense of not quite knowing what’s real and what’s imagined takes the movie pretty far, but after Nina’s first major meltdown, a scene that employs several overused and unconvincing scary movie tricks, the intrigue of Nina’s questionable sanity wears thin and the film becomes less of a psychological thriller and just plain psycho. There are some breathtaking and unexpected moments (like Nina’s stunning metamorphosis into the the black swan, feathers and all), but BLACK SWAN is at its best when it stays focused on Nina’s mental and professional struggle without trying to be a scary movie too; Watching Portman battle Nina’s demons is thrilling enough.