Iris (Emily Blunt) lays in bed with her sister, Hannah (Rosemarie DeWitt) in Your Sister's Sister.
Your Sister's Sister is writer-director Lynn Shelton's attempt to put an uber-realistic, mumblecore spin on a story that's more than a little artificial. The end result is a film that wanders purposelessly toward a goofy conclusion. There's talent on display—no doubt about it—but it never manifests itself into anything resembling a satisfying movie.
At the heart of Your Sister's Sister is a love triangle of sorts. Jack (Mark Duplass) is drifting through life following the death of his brother, Tom. His best friend is Iris (Emily Blunt), and following an outburst by Jack at a memorial get-together for Tom, she sends him to her family's cabin in the Washington wilderness. While there, Jack meets Hannah (Rosemarie DeWitt), Iris' older sister, who, like Jack, is seeking solitude. She's just broken up with her partner of seven years, and Jack consoles her while the two down tequila. One thing leads to another, and their night ends in bed together.
To the surprise of both, Iris arrives the next day. She's thrilled to see her sister and confides in her immediately that she thinks she has real feelings for Jack. So Hannah and Jack agree to keep their tryst a secret.
Your Sister's Sister features a few standout scenes—like Jack and Hannah's late-night drinking binge. It's during moments like these that the film's substance and style align. When Shelton's film isn't dragging its feet to get these characters to certain emotional places, it's a good one. This sloppy storytelling is pervasive, however. Unless Shelton's goal was to make a movie about damaged people sitting around and drinking for 90 minutes, she needed to plot it the way she did. But that doesn't make it any more believable.
The ending, in particular, is a big problem. Ambiguity is fine if there's a legitimate artistic reason to leave an audience hanging. It's hard to imagine why Shelton felt no closure was a better option than closure. Even beyond the controversial final shot, the final 15 minutes of this film are almost comical. The people who start this film are not the same who finish it, which is great. Films like this need their characters to grow or change. But the evolution of Hannah, Iris, and Jack is so accelerated that it feels downright silly.
The casting of Emily Blunt, a typically reliable performer, is arguably the film's biggest misstep. Her line delivery is stunted; She overacts certain scenes. Though appropriately adorable, she just doesn't fit in with more naturalistic performers like Duplass and DeWitt (who, incidentally, are pretty good).
Shelton earned a great deal of respect (if not money or clout) following 2009's Humpday—a better film that's nonetheless stylistically similar to Your Sister's Sister. She clearly has a niche—one in which individuals like the Duplass Brothers coexist. Your Sister's Sister, unfortunately, is just a blip. Of all the great uber-low-budget American indies we've seen over the past decade, this is among the more forgettable, and coupled with the epic disaster that was Jeff, Who Lives at Home earlier this year, fans of the mumblecore genre have reason to worry. But here's hoping it's merely a temporary rough patch and that these filmmakers can turn things back around next year.