Most low-budget independent films that seem improvised, from the heyday of John Cassavetes to the so-called mumblecore movement, were in fact carefully scripted. Generally, you can tell you’re watching actual improv because the actors seem vaguely uncertain, too intent on figuring out what they should say next to exist in the moment. Up-and-coming director Lynn Shelton, however, seems to have miraculously worked out a method for creating wholly credible conversations and behavior out of thin air while the camera’s rolling. Her latest film, Your Sister’s Sister, isn’t quite as accomplished as her previous effort, Humpday, but it still confirms her as a hugely promising talent.
Like Humpday, which was about a couple of straight dudes who toy with the idea of having sex together for an art project, Your Sister’s Sister pivots on sexual transgression. Still reeling from the death of his brother a year earlier, Jack (Mark Duplass, who’s everywhere right now) heads for the isolated cabin owned by the family of his platonic friend Iris (Emily Blunt), discovering only when he arrives that it’s already occupied by Iris’ sister Hannah (Rosemarie DeWitt), equally despondent after having just ended a long-term lesbian relationship. Booze flows, tongues wag, and when Iris unexpectedly shows up the next morning and tells Hannah of her secret attraction to Jack ... well, perhaps you can guess how the situation might have been complicated the night before.
The interaction among the three characters is the entire film, and Duplass, Blunt and DeWitt make those characters excitingly vivid, talking to each other in a discursive, off-the-cuff way that never once degenerates into affected mannerism or rudderless wheel-spinning. Every interaction feels just right, utterly believable but in an entertaining way; even when someone’s behavior seems contrived to narrative ends, its specific manifestation never does. Only trouble is, Shelton has no exit strategy—what should be the movie’s third act collapses into an unbelievably lazy montage set to a noodly guitar score. The sense of filmus interruptus is frustrating, but even if Your Sister’s Sister is 90 percent setup for a payoff that never arrives, every moment crackles and sparks. That counts for something.