Your Sister's Sister (15)

Lynn Shelton's comedy of romantic distress feels effortlessly charming, cracks some good jokes but finally delivers much less than promised.

Jack (Mark Duplass), grieving on the first anniversary of his brother's death, is packed off by his best friend Iris (Emily Blunt) to her family's island retreat for rest and recuperation. There he finds Iris's sister Hannah (Rosemarie DeWitt) unexpectedly installed, recovering from the break-up of a seven-year relationship.

Having bonded over dirty talk and tequila they roll into bed and scramble out the next morning upon hearing Iris arrive. Their secret night together ticks away like a timebomb under the kitchen table, primed once Iris makes her own confession to Hannah. The three leads handle the semi-improvised script with panache, and in the case of Blunt and DeWitt really convince as sisters driven by love and latent rivalry. L

ess challenging and funny than Shelton's previous Humpday, the film retreats from its initial edginess into something comfortable and slightly glib, a study in self-absorption that lets off its characters too easily.