YOUR SISTER’S SISTER “Okay, ladies. How’re my chances looking for a threesome? No pressure.”

SEATTLE DIRECTOR Lynn Shelton's new movie opens with a meltdown: Jack (Mark Duplass) is a sad sack of a guy who commemorates the one-year anniversary of his brother's death by drunkenly shouting at the friends who insist on romanticizing his dead sibling. Afterward, he's cornered by his best friend Iris (Emily Blunt), who firmly instructs him that after a year of grieving, it's time to get his head together. She sends him off to enjoy some quiet time at her family cabin, but solitude isn't on the agenda: Jack arrives to find the house already occupied by Iris' half-sister, Hannah (Rosemarie DeWitt), who's drowning her own breakup-related sorrows in tequila.

Jack pulls up a shot glass and joins Hannah for a drink, and eventually booze so sufficiently corrupts good judgment that Hannah, a lesbian, hits "override" on her sexual orientation for just long enough to hop in bed with Jack. (Those who object to another movie featuring a lesbian sleeping with a man—à la the 2010 lesbian family drama The Kids Are All Right, which had a similar premise—may be somewhat soothed to learn that Jack doesn't exactly distinguish himself in the bedroom department, and Hannah initially regards the whole thing as a meaningless, booze-fueled experiment.) When Iris arrives the next morning, things get messy—between the sisters, different in age and temperament, and between Iris and Jack, whose feelings for each other are complicated by the fact that Iris used to date Jack's dead brother.

Most of My Sister's Sister is about interpersonal relationships, about characters figuring out who they are in relationship to one another, even when things get weird. It's disappointing, then, when the plot takes a Jerry Springer-esque turn three-quarters of the way through—as though Shelton lost faith that the tension generated by these complex relationships alone was sufficient to get the characters where they needed to go. In the end, though, Your Sister's Sister is really about people who care about each other, doing their best to push through stuff that seems impossible to overcome in the interests of creating—and preserving—a family. It doesn't exactly carve out new territory, but it explores these questions of family and growth with intelligence and charm.