Your Sister’s Sister

Rated 3.0

A drunken one-night stand between a man (Mark Duplass) and the lesbian sister (Rosemarie DeWitt) of his best friend (Emily Blunt) leads to unexpected complications when the sister turns out not to have been too drunk for selfish conniving. Director Lynn Shelton gets a writing credit as well, but in fact all four speaking actors (the other is Mike Birbiglia in a small but key bit in the first scene) get “creative consultants” credit—meaning their dialogue was entirely improvised within Shelton’s basic framework. The framework may be contrived and mechanical, and some of the perceptions we get may have been unintended, but there are pleasures in improv when the players are as sharp and canny as they are here. Shelton planted this garden patch and tended it while it grew, and that’s a kind of writing too.