Altitude Film Sales has boarded international sales rights for Tribeca hit The Boy Downstairs, starring Zosia Mamet and Matthew Shear, and will be shopping the project to buyers in Cannes this month. The company’s distribution arm, Altitude Film Distribution, has taken UK rights to the title. UTA is repping North American rights.

Project marks the feature debut from writer-director Sophie Brooks and is produced by Cliffbrook Films’ Dan Clifton (The Belko Experiment), David Brooks (ATM) and Motion Picture Capital (Hampstead) with exec producer Paul Brooks (Pitch Perfect, My Big Fat Greek Wedding). The UK distribution deal was struck by Altitude’s co-CEO Andy Mayson with Motion Picture Capital, the major financier of the film.

In the film, Mamet plays Diana who moves back to New York City after a few years in London and finds what seems to be the perfect Brooklyn apartment to start fresh. However, on the first night in her new home she discovers her ex-boyfriend Ben, played by Shear, lives in the apartment below. After an awkward first encounter, Diana proclaims her intentions for a genuine friendship but as the story progresses and old wounds are reopened she is forced to confront the true nature of her feelings.

“It’s great to be working with Cliffbrook Films, Paul Brooks and Motion Picture Captial to bring Sophie Brooks’ striking debut to audiences here in the UK,” said Altitude Film Entertainment Chairman and co-CEO Will Clarke. “Zosia Mamet is a truly exciting rising star and her touching performance in The Boy Downstairs, wonderfully celebrated at Tribeca, will further cement her rise to stardom.”

Mamet is best known for her role in HBO series Girls. She recently completed production on David Robert Mitchell’s Under the Silver Lake opposite Andrew Garfield and riley Keough and featured in Todd Solonz’s Weiner-Dog, Diane Bell’s Bleeding Heart and Lisa Cholodenko’s The Kids Are All Right. Shear will next be seen in Noah Baumbach’s The Meyerowitz Stories with Dustin Hoffman, Ben Stiller and Emma Thompson which is premiering in competition in Cannes. He’s currently in production on TNT’s new series The Alienist, in which he stars opposite Luke Evans and Dakota Fanning.

Mamet is repped by UTA. Shear is repped by ICM.