Your Sister’s Sister (2012)

Drama Rated R

Writer-director Lynn Shelton is diabolical in her devising of predicaments that will make her characters squirm. You almost resent her for putting you through the experience of watching, except that she mines deep emotional reservoirs and comes out with observations about human nature that otherwise wouldn’t have been possible.

Humpday took a titillating concept – What if a pair of male, heterosexual best friends agreed to have sex on film for an amateur porn contest? – and used it to make us think about masculinity, homophobia, marriage and maturity in completely different ways. Your Sister’s Sister is less expansive – its observations don’t echo quite as far beyond the trio at its center – but it’s still an enriching if discomforting look at the fault lines that lie beneath human relationships.

Mark Duplass, a writer and director in his own right, as well as one of the stars of Humpday, reteams with Shelton to play Jack, a scruffy thirtysomething grieving the death, a year earlier, of his brother. Jack is still close to his brother’s former girlfriend, Iris (Emily Blunt), who suggests he spend some alone time in her family’s island cabin. Solitude evades him however, what with Iris’ stepsister Hannah (Rosemarie DeWitt) already at the cabin and Iris herself showing up the next day.

Your Sister’s Sister is a chamber piece among these three, as misunderstandings, deceptions and confessions reverberate among them. All of the actors are excellent, especially when DeWitt and Blunt are sharing moments of sisterly honesty. Duplass is, out of narrative necessity, a bit of a third wheel, until he gets a climactic speech that’s somehow fatherly, friendly and romantic all at the same time.

That sort of uncomfortable mishmash is appropriate, for this is mostly what Your Sister’s Sister is about: our desire for family, however unconventional. There are allusions throughout to ways that each of these characters have had their respective families torn apart. Now, in this cabin, on this island, they’re fumbling about trying to construct one of their own.