Greta Gerwig shifts from sincere to silly on disproportionately long legs that suggest those of a flamingo. Her wide-set, hazel eyes are focused, contradicted by flighty arms that say screwball and, sometimes, screw-loose. After about a dozen movies in half as many years, Gerwig is shaping up as the Jill Clayburgh of Generation Y. That is to say: offbeat, angsty, and endlessly watchable.

Sadly, the same cannot be said of Lola Versus, an unfinished portrait of an unfinished womanchild with fidgety poise nicely embodied by Gerwig. Lola, a graduate student in a long-term relationship, abruptly becomes unmoored by the approach of her 30th birthday, the defection of her fiance, and the existential panic of a future with more variables than she had bargained for. The breakup precipitates not a breakdown, but a meltdown.

From this not-unpromising starting point, screenwriters Daryl Wein and Zoe Lister Jones (who also costars) serve up a directionless identity comedy that fails to harness itself to Gerwig's delirious comic momentum. Lister Jones, a petite and brittle brunette, who looks as though she would be the ideal foil for Gerwig's rangy, sensitive blonde, is stridently unfunny as Lola's best friend, Alice.

Like its title character, Lola drifts from romantic storm to any-port-in-a-storm, almost perversely steering clear of the safe harbor represented by Henry (Hamish Linklater), the smitten best chum of Lola's ex, Luke (Joel Kinnaman). Lola, who is writing a doctoral dissertation, moonlights as a waitress at a bistro owned by her parents (Debra Winger and Bill Pullman). Much of the film is taken up with Lola's other nocturnal activities that include dating, clubbing, dancing, and drinking.

For Lola, random is not just a noun and adjective, it is a lifestyle. For Lola Versus, random is a compendium of bad dates, bad sex, self-pity without self-awareness, and Gerwig's captivating presence. Bottom line: She is a charming actress in a charmless picture.

At 24 minutes, Lola Versus might be a middling episode of a sitcom like New Girl. At 87 minutes, it is a gracefully aimed arrow shot in the air. Where it lands, Wein and Lister Jones know not where.EndText