There’s probably not a good time for a man to question a group of mourners’ rosy memories of his brother, but a memorial service, even one a year removed from the brother’s death, must count as one of the least appropriate times. Yet something compels the aimless protagonist played by Mark Duplass to do just that in the opening scene of Your Sister’s Sister, Lynn Shelton’s follow-up to her justly acclaimed uncomfortable sex comedy Humpday. It isn’t just some perverse urge making him sour the party, either. After a fellow mourner (Mike Birbiglia) tells a moving story about seeing Hotel Rwanda with his late friend, who was moved enough by the movie that he started volunteering, Duplass counters with his own moviegoing story, recalling his brother as a bully who changed his ways after seeing Revenge Of The Nerds. But not for the right reasons: He just figured that if the nerds and outcasts ultimately triumph, he might as well be on winners’ side.
The awkward moment reprises some questions that helped make Humpday so compelling: How much of who we are is situational? How much can we change our identity when called upon to play different roles? And once we change, how much of our old selves can we reclaim? For a while, it looks as if Your Sister’s Sister will delve even deeper into the issues raised by those questions. Hoping to cure his seemingly permanent funk, Duplass’ best friend (Emily Blunt) sends him packing to her family’s isolated island summer home. But instead of solitude, Duplass finds Blunt’s half-sister (Rosemarie DeWitt), who’s in the midst of drowning her sorrows after breaking up with her girlfriend of seven years. When Jose Cuervo and self-pity overwhelm them, Duplass and Dewitt sleep together. The next day, Blunt shows up and they decide to keep their one-night stand to themselves, at first at Duplass’ insistence, and later for reasons DeWitt can’t share.
It’s a farcical but low-key setup that, for a while, Shelton and her cast play for all it’s worth, creating intimacy and discomfort in equal measure as the characters spend time together, the sisters dredging up old embarrassments as Duplass attempts to figure out where he stands with each. It’s potent and funny, aimless, but with a lot to say about how people define themselves. (DeWitt reacts to her one-night stand with a shrug of regret, but responds furiously when she’s tricked into breaking her vegan diet.) But once the film does settle on a trajectory, it loses its way, paying off its investment in its characters with a whopper of a contrivance, a montage sequence long enough to train Rocky twice, and a conclusion that tidies up all that carefully cultivated chaos much too neatly. This time out, Shelton seems to be playing the part of someone who doesn’t know how to finish what she started.