Your Sister's Sister is a neat little one-acter whose improvisational dialogue is more likely to elicit wry chortles at the realism of sibling dynamics rather than the raucous guffaws that accompany rapier wordsmithery. Blunt plays Iris, girlfriend of the recently passed Tom and best friend to his brother Jack (Duplass), who offers him a secluded spot of head-clearing at her father's remote cabin in the woods. There he meets Hannah (DeWitt), Iris' gay and newly ex-long-term-relationshed sister. A bottle of tequila does the rest. Such an unfussy storyline turns what might have been a muddle of half-baked unscripted awfulness into a sharply observed piece of naturalism, even if at times you're aware of the one-note tune. In fact, most of the joy is derived from watching the three leads career into and dodge each other's fears and neuroses like pinball ball-bearings, so much so, that one feels the palpable weight of clunky narrative resolution as the story attempts to resolve. On stage, with the immediacy of its live surroundings, this would have made for a spellbinding hour or so, up on the screen, it feels ever so slight.