As viewers said goodbye to HBO original series Girls, Zosia Mamet’s Shoshanna Shapiro seemed confidently on her way to a new life—and so, it seems, is Mamet, appearing at the Tribeca Film Festival in support of Sophie Brook’s feature directorial debut, The Boy Downstairs. Told partially in flashbacks—watching the inception and eventual disintegration of a romantic relationship—the film tells the story of Diana (Mamet), a socially uncomfortable New Yorker who’s just doing the best she can, confronting frustration, awkwardness and a sense of profound loss.

Moving back to New York from London—akin to Shoshanna’s emotional journey back home from Tokyo—things seem to be going well for the fledgling writer, as she manages to lock down a stellar apartment in the city, until the realization hits her: Her ex-boyfriend and first love lives in her building, in the apartment downstairs.

“When I first read the script, I was in New Mexico with my husband, who was shooting a movie, and he had a really early call, and so we’d gotten in bed early, and I was like, ‘Well, I’m not ready to go to bed, so I’ll read this script my agent sent me,’ Mamet explained, sitting down with co-stars Matthew Shear and Sarah Ramos, and director Sophie Brooks at Deadline’s Tribeca Studio. “He had to go sleep in the living room, because I was laughing and crying so audibly that I was keeping him awake, and I couldn’t remember the last time I read a script that made me react so viscerally, just by reading it.”

Jon Pack

“That was really the first time I fell in love, and I was so intrigued by this character that we root for so much, but is also so flawed, in so many ways, and just how real this romance was that Sophie had written, and this period of time in your life,” the actress continued.

The singularly painful and moving romantic comedy hinges on the continually awkward dynamic between Diana and Ben (Matthew Shear), wh0 have to learn how to co-exist, and let sleeping dogs lie, something that is particularly difficult for Diana to do, coming into confrontation with Ben’s new girlfriend, Meg. “I think just the confrontational set-up of this guy living in the same building as his ex-girlfriend just allowed automatically for so much awkward tension and double-takes,” Shear said. “It was exciting for me to revisit old romantic wounds, and to really get to revel in that.”

Approaching the role of the contemptuous new girlfriend—who senses Diana lingering around her apartment—Sarah Ramos was challenged, finding herself relating much more to Mamet’s character than her own. “I feel like I related to Diana more, so I was thinking about for Meg, what kind of character would drive me crazy, to be my ex-boyfriend’s new girlfriend,” she said. “We talked about her life being put together, or seeming put together—the worst.”

“You were so perfect, and it just made my skin crawl, in the best way,” Mamet beamed.

To view Deadline’s conversation with the creative team behind The Boy Downstairs, click above. Upcoming Tribeca showtimes for the film can be found here.