Beginning with a bilious toast and ending with a group hug, Lynn Shelton's Your Sister's Sister, her fourth film, expertly makes us squirm for about half its running time only to soothe us with empty pop-psych declarations. In Shelton's previous feature, the bolder Humpday, two straight guys, in a moment of perverse macho posturing, agree to do it with each other on camera, but Your Sister's Sister loses interest in the sexual awkwardness and anxiety and uncomfortable truths it sets up. Still, with each character in its central romantic triangle hiding a secret, the dialogue in Your Sister's Sister is often a funny combination of stammers, overexplaining, and nervous backtracking. This anodyne-by-design talk often gives way to lacerating revelations: "There'll be no talking behind anyone's back in this house," declares Jack (Mark Duplass, one of Humpday's dare-taking hets) at breakfast in the idyllic cabin he winds up sharing with half-sisters Iris (Emily Blunt) and Hannah (Rosemarie DeWitt), who, self-medicating with tequila after leaving her girlfriend of seven years, has abysmal 90-second sex with Jack. In these moments, the largely improvised script works well, exposing the jabs and parries of passive-aggressive behavior. It all unravels—rapidly and inexorably—however, becoming another movie entirely, filled with montages of cuddles, walks in the woods, and a regressed man's epiphany in a diner—a "healing" arc nearly indistinguishable from that found in nearly every comedy hybrid playing in multiplexes. This softening is all the more disappointing when compared with Humpday's closing scenes, which were ambiguous, discomfiting, and messy, just like the two characters at its center.