Ringed by a band of scrutinizing Wall Street yuppies at a dinner party where she doesn't belong, Frances (Greta Gerwig) is asked the inevitable "What do you do?" question.

"It's kind of hard to explain," she responds, warily.

"Because what you do is complicated?" wonders her inquistor.

"Because I don't really do it," Frances explains.

Frances Ha, a collaboration between Gerwig (actress and cowriter) and Noah Baumbach (director and cowriter), achieves a kind of pivotal moment of awkward wisdom, and revelation a few minutes later at that same dinner table. Frances - a 27-year-old dancer whose hopes and dreams are dashed with the regularity of changing traffic lights - blurts out a philosophy that startles and stupefies the other guests.

Her honesty is beautiful.

So too is Frances Ha, a black-and-white salute to the French New Wave (the score is borrowed from Georges Delerue, composer of many a Truffaut and Godard film) that manages to be very much of this moment, tracking a spirited stumblebum as she navigates (or fails to navigate) the post-college New York world of roommates, boyfriends, jobs, and money woes.

At first, all seems blissfully, slackerfully right with Frances. She shares an apartment (in Brooklyn, of course) with Sophie (Mickey Sumner), her best friend from their Vassar days. They share their most intimate thoughts. They cuddle and clown. They are, as Frances quips, like "an old lesbian couple that doesn't have sex anymore."

But inevitably, Sophie and Frances begin to drift apart - although Frances is in denial about it. Sophie has a serious boyfriend, and serious plans, and a serious place in Tribeca. And so Frances moves in and out of a succession of apartments, on the run - from herself, and who she wants to be. For a while, she settles in with Lev (Adam Driver) and Benji (Michael Zegen), a pair of chirpy hipsters. She promises to pay her fair share of the rent when her dancing career picks up.

It doesn't pick up.

Baumbach (The Squid and the Whale) first cast Gerwig in Greenberg, opposite Ben Stiller. She's the gofer/dog walker/nanny who upends the house-sitting, sourpuss Greenberg's life, and she's great. The actress - who had been writing and starring in low-budget, low-expectation "mumblecore" projects - is funny in ways that are completely unforced, uncompromised.

In Frances Ha, she is funny, too, but she's also like the weather in Ireland: four seasons in one day. Sad, silly, clumsy, graceful, inappropriate, perfect.

Frances Ha **** (out of four stars)

Directed by Noah Baumbach. With Greta Gerwig, Mickey Sumner, and Adam Driver. Distributed by IFC Films. Running time: 1 hour, 25 mins.

Parent's guide: R (profanity, adult themes)

Playing at: Ritz Five EndText