Yet another gathering of casually dressed, cusp-of-30 urbanites with self-effacing humor, "Your Sister's Sister" follows the indie-cinema blueprint to the letter with one exception: One of the film's characters is a lesbian.
She is Hannah (Rosemarie DeWitt), and she's treated as a rather exotic specimen, which she sort of is in the largely heterosexual world of independently made movies. Early in the film, Hannah takes a brief departure from her usual preference, which the movie considers an outrageous moment of envelope-pushing hilarity. It's really just a tiny point on which to pivot a tiny plot, but "Your Sister's Sister," like so many films in this genre, is always thinking small.
The ubiquitous Mark Duplass (appearing in at least three films this month, including "Safety Not Guaranteed" and the upcoming "People Like Us") plays Jack, whose dead brother used to date Iris (Emily Blunt). Depressed and grieving, Jack accepts Iris' offer to hole up alone in a remote family cabin, but it's already occupied by her sister, the attractive and slightly abrasive Hannah. Following a few tequilas and a crude come-on from Jack, they hit the sack. But wait! Here comes Iris to tell him she's secretly pining for him.
Why, exactly, is unclear. Duplass' charmless, clueless Jack seems a poor match for Blunt's quick-witted Iris, not to mention DeWitt's formidable Hannah. (The movie is almost entirely improvised, an admittedly impressive feat.) But if the emotions on-screen don't convince you, writer-director Lynn Shelton ("Humpday") inserts wisftul guitar-pop to let you know what to feel. "Your Sister's Sister" is convinced of its own depth but ultimately feels superficial -- rather like its inexplicable title.
PLOT A grieving man seeks solace in two sets of arms. RATING R (language, sexuality, adult themes)
BOTTOM LINE Another indie flick: Long on talk, short on character, with jangly guitar-pop to tell you what to feel.