An intimate character study, Lynn Shelton's Your Sister's Sister benefits from three solid lead performances that capture the nuances in her deceptively straightforward script.
Mark Duplass stars as Jack, a lost young man still mourning his brother's death a year later. His best friend Iris (Emily Blunt), who also happens to be his brother's ex-girlfriend, orders him to get away from it all by going to her family's secluded cottage and getting his head straight. When he arrives, he discovers that Iris' half sister Hannah (Rosemarie DeWitt) is already there. They have an awkward initial meeting, but that night they end up sharing a bottle of booze and baring their souls to each other -- she's getting over the end of a lengthy romance with a former girlfriend -- which eventually leads to drunken sex. Iris unexpectedly shows up the following morning, and Jack wants to keep the activities from the night before a secret because he's in love with Iris, even though he can't quite admit it. Over a couple of days, each of these three people will reveal hidden motivations, reopen old wounds, and try to figure out what it is they really want.
Growing steadily over the course of her first few films, Shelton flowers as a writer and director with Your Sister's Sister. The characters' flaws are as apparent as their strengths, and although the plot structure seems obvious in retrospect, the understated performances and the actors' conversational tone make it seem that everything happens because of choices these characters are making rather than the choices a screenwriter is making.
Duplass isn't afraid to play up Jack's most annoying traits. He appears to be as lazy as he is heartbroken, and he's quick to assign blame to others while deflecting it from himself; however, he's also a charming guy who is eager to help those who feel as bad as he does. Emily Blunt gives Iris a specificity that helps ground what is probably the least fleshed-out character in the piece. She seems to exist only in how she reacts to Jack and Hannah, but Blunt makes her idiosyncrasies feel like traits rather than quirks, and she has beautiful wide eyes that compellingly communicate intense romantic longing. However, it's Rosemarie DeWitt who ends up dominating the movie -- largely because she has the best part. Hannah is sphinxlike much of the time -- we're not sure exactly what she wants -- until a major plot point is unveiled and we finally understand why she's behaved as she has.
Shelton develops a sense of intimacy in this film, both as a writer and a director. She frames the actors purposefully, but naturally -- when characters share the screen and when they don't reveal a great deal. It's a small movie that works because everyone is on the same page tonally, and Shelton understands exactly what she's doing dramatically in every scene. She knows how to move the story along while capturing the feeling that these imperfect people are making up their lives as they go.