Lynn Shelton’s fourth and latest feature, Your Sister’s Sister, again pairs her with Mark Duplass, for a surprisingly rigorous examination of the boundaries separating friendship and romance. 2009’s Humpday scrutinized the concept of bromance with an intensity perhaps unmatched by any movie since Ken Russell’s Women in Love—but Shelton's pseudo-naturalist repertoire of meandering dialogue (littered with “awesome”’s and “dude”’s), obligatory-feeling party scenes, and handheld DV cinematography (shoestring budget plainly visible), is night-and-day with Russell’s arsenal of delirious excess and unfettered carnality. Indeed, Your Sister’s Sister is a step into formulaic melodrama that restricts itself to the maddening ambiguities and repressed yearnings bound up in the fabric of any close relationship.

Jack (Duplass) is first introduced as a straight-talking depressive who uses a small gathering on the one-year anniversary of his brother’s untimely death as an opportunity to rain all over his friends’ sugarcoated parade of tipsy toasts and warm reminiscences. His closest buddy, Iris (Emily Blunt), reads Jack’s act of revolt as a cry for help and ships him off to her family’s cabin in the serene forests of an anonymous island off the coast of Washington.

Bicycle in tow, Jack arrives on the cabin’s porch and, one comic misunderstanding later, meets Iris’s half-sister Hannah (Rosemarie DeWitt), who has herself sought refuge there in order to recover from her break-up with the never-named woman she’d been with for the past seven years. The aftermath of a 3:00 a.m. tequila-fueled tug-of-war lands arch-dude Jack in bed with mixed-up Hannah for a typically awkward sexual encounter that both will come to regret when Iris arrives unannounced the next morning. A number of twists and turns follow, yielding a digestibly windy plot conveyed through a combination of shaggy-dog wit and not-so-subtle emoting.

Shelton’s shift away from the necessarily sloppy sensibility exemplified by Duplass’s own The Puffy Chair (2005) is marred by a handful of stylistic affectations that suggest pandering. An intrusive score won’t leave us alone, needlessly reminding us of the easily intelligible narrative’s emotional resonance. The frequent pillow shots of nature come off as filler rather than Ozu—the majesty of the Pacific Northwestern wilderness is simply of less interest here than the cleverly written/improvised banter shared by Duplass, Blunt, and DeWitt.

The two lead actresses give inoffensive performances as semi-siblings whose latent antagonism serves as a trampoline for Duplass’s signature shtick. Yet their very presence seems resolutely out of place, yielding a persistent sense that the film constitutes an awkwardly constructed “girls vs. boy” parable. This tension is curiously reflected by Shelton’s own place within the recent history of mumblecore: while her peers (Joe Swanberg, Andrew Bujalski, Kentucker Audley, et al.) have chosen to burrow further underground in order to unearth new directions for their collective aesthetic, Shelton (like the Duplass Brothers) has instead gravitated toward something more closely resembling the codified, bankable forms of thoughtful comedy found in the output of the Judd Apatow camp.

However, the stench of formula only comes to taint the whole film in retrospect, and the work itself is funny and affecting enough to veil many of its formal shortcomings. But one wonders whether these results couldn’t have been achieved more successfully through a pared-down construction that isn’t as concerned with moving its audience by any means necessary. As for Shelton’s decision to end the film on a cliché cliffhanger…