'The Boy Downstairs' review: Zosia Mamet shines in her post-'Girls' film

As the dust settles from Girls' final season, culture watchers will likely do as they did after Sex and the City: Follow the four leads through their next projects, tracking them against one another. 

There is, of course, some foolishness to this. Success and failure don't happen in such a bubble. Allison Williams getting projects doesn't mean Jemima Kirke won't. Plus, since Lena Dunham has so many nonacting ventures, it's already an uneven field. But it's also hard to ignore how, say, Cynthia Nixon thrives while Kristin Davis doesn't.

One of the first post-Girls projects out of the gate is Zosia Mamet's The Boy Downstairs, which premiered at the Tribeca Film Festival Sunday. It's the kind of quiet indie dramedy that feels like pure festival fare: Boy and girl traverse difficult breakup trauma years after they split when girl accidentally moves into boy's apartment building. It's very New York and very quietly charming. But Mamet elevates the entire thing through a performance that brings every bit of what she learned playing Shoshanna Shapiro and adds beautiful new layers.

Zosia MametJamie McCarthy/Getty Images

As Diana, a writer returning to New York after years in London, Mamet plays humanity over quirk. She's not your typical indie dramedy heroine, spouting off wise bon mots while somehow also being a disaster in her personal life. Instead, Diana is smart and accomplished but having trouble finding drive when she returns home. It's like if the Rory Gilmore story in Gilmore Girls: A Year in the Life had been more fleshed out.

In the kind of story that will make New Yorkers pant with envy, Diana finds a perfect apartment, with a landlord you could only dream of. The problem: After she moves in, she learns her ex-boyfriend Ben (played beguilingly by Mistress America's Matthew Shear) occupies the basement apartment with his new girlfriend. Director/writer Sophie Brooks, who is making her feature debut with The Boy Downstairs, avoids depicting awkwardness through hijinks, instead depicting Diana slowly self-sabotaging. It's cringe-worthy in how relatable it is.

The Boy Downstairs gets less interesting the more it pivots away from Diana and Ben, offering small plots about Diana's landlord and best friend. While it's nice to see into these supporting characters' interior lives, they ultimately don't offer much to the plot. But when the movie homes in on its leads, particularly in flashbacks to Diana and Ben's breakup, it — and Mamet — are never better.

Matthew ShearCharles Sykes/AP

As The Boy Downstairs takes its world premiere bow, some will ask whether this is Mamet's next big moment. A lot of that is beyond her, based on distribution and how much buzz a B+ movie can get for an A+ performance. She's also got several other projects either in the can or lined up, so she's likely set even if nothing comes of this.

But as Diana, Mamet proves her work as Shoshanna was no fluke. She's a remarkable dramatic actress with charm and wit to play the funnier moments, too. The Boy Downstairs succeeds as a showcase for her stardom. Brooks' movie may not have worked without her.

The Boy Downstairs is playing throughout the Tribeca Film Festival. Times and rush ticket details are available on the festival's website.

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