Lynn Shelton is quickly becoming one of my favorite indie film artists. Her writing and directorial offerings are somewhat relegated to the fly-on-the-wall hipster “mumblecore” category, but what separates Shelton is her narrative momentum, her laser-like focus with character, and her sense that a movie needs to build to something significant. With 2009’s Humpday, it was two dudes who might have sex as a test of their masculinity (you really need to see the movie for the full context). With Your Sister’s Sister, it’s the full ramifications of a bunch of delicious relationship secrets getting out there. Everyone in the film has something to hide and something to lose, and watching it all play out with humor and sweetness and honesty that is rare in movies.

Jack (Mark Duplass) is still coming to terms with the death of his older brother. His best friend, Iris (Emily Blunt), who was his brother’s girlfriend at the time of his passing, offers a suggestion. She arranges some alone time for the guy to clear his head. He bikes out to her family cabin but is surprised to find a guest already there, Hannah (Rosemarie DeWitt), Iris’ older sister. Hannah and Jack break the ice by bonding over their personal loss: his brother and her ending a seven-year relationship with her girlfriend. Over a long night of drinking, the two decide to impulsively have sex. The next morning is even more awkward when Iris shows up at the cabin, planning to finally reveal her own feelings for Jack. What follows may be one of the few character-based sitcom plots I’ve witnessed.

Much like Shelton’s previous movie, the greatest strength of the film is how beautifully naturalistic it all feels while still telling an engaging story. The film has a relaxed vibe that washes over you, allowing you to immerse yourself in what feels like a real group of friends. There’s a tremendous naturalistic ease the film exudes, with the actors so familiar with one another that they truly feel like family. When I have well developed characters, and actors who seem so knowledgeable of their character’s tics and flaws and secrets and smallest details, I could honestly listen to them talk for hours. I don’t want to mistakenly give the impression that this movie is a dull yakfest where the participants are in love with the sound of their own exceptional voices. Each scene in this movie advances the plot further, twisting the screws, complicating matters, and brimming with delightful awkwardness and tension. With 2009’s Humpday, I wrote: “What I really appreciated about Humpday is that every moment feels genuine and every scene has a point. I was amazed that Shelton and her small unit of actors had made it so that every conversation had purpose; there is so little fat to this screenplay. Each scene reveals something new about a character or pushes the narrative forward toward its uncomfortable climax, and each moment never breaks the reality of the story.” And the same can be said for Your Sister’s Sister as well.

While the premise is a bit of a sitcom novelty with some farcical developments thrown in, the depth of the characters and the fantastic acting help to make sure that Your Sister’s Sister is nothing but graceful and beguiling. And the escalating conflicts, personal revelations and complicated feelings, always find a way to come across as organic to the story. That’s another amazing part of the film, that even with all the sexual hijinks that it still manages to feel grounded and surprisingly relatable. These are interesting, complicated, flawed, and spectacular characters, and watching them interact, profess their love through small actions and big declarations, seeing their heartfelt camaraderie, and watch them navigate their troubled lives to find some semblance of a happy ending is a joy to watch. This is a potent little movie, fully realized, poignant, funny, and genuine.

The film was shot over the course of 12 days and Shelton has said that much of the dialogue was improvised, working off her outline. Improvisation is a dangerous tact when dealing with a dialogue-driven film, such as this one. Just because it’s coming off the top of your head doesn’t mean it’s going to sound good. Not everyone is gifted with the ability to improv dialogue that is true to character, revealing, advances the story, as well as just being entertaining. Luckily, Your Sister’s Sister is the exception.

If Your Sister’s Sister does have a weakness, it’s the third act that seems to stall out without giving us much in development before tidying the broken relationships up again. The film’s comedic structure could feel, in lesser hands, like a generic sitcom. It is to Shelton and her actors’ credit that the twists and turns still manage to feel as believable as possible. The third act hits when all the secrets come out, pushing the characters away. Rather than (minor spoilers) ramping things up, we merely endure an extended wordless sequence of images of Jack biking around and the sisters burying the hatchet. Then it’s time for our big happy romantic declaration that tidies everything up, and we’re done. While satisfying on an emotional level given our empathy for the trio, the third act does seem very thin for an otherwise lean and well-structured story. It feels like perhaps Shelton only had enough plot for two acts.

The main trio is a rather engaging ensemble that convincingly plays a besotted group of friends and family. Duplass (Safety Not Guaranteed) has gotten considerably more attention since starring in Shelton’s last movie; the man and his schlubby, smirky charm are ubiquitous. He has a way of being edgy without pushy and nonplussed and flummoxed without going overboard. Duplass has a natural fit for comedy but the man can really excel with the meatier drama bits as well, displaying the painful yearning of a man caught between his desire and the need to move on. He’s a winning and likeable presence that can still be endearing even when he’s flailing around or making others uncomfortable.

DeWitt (The Watch) was a late addition to the cast, replacing Rachel Weisv (The Bourne Legacy) when scheduling conflicts got the best of her. She deserves extra kudos for how good she is considering the miniscule prep time she had compared with her costars. DeWitt is amusing in how cagey and sardonic she can be, and her chemistry with Blunt (Looper) is outstanding. I greatly enjoyed the subtle nuances between them, the way their body language and gestures added extra layers to their relationship, the familiar communication and sisterly code, and just the smallest details that felt well thought out. The relationships in Your Sister’s Sister feel sweetly genuine, and with the benefit of great actors, it lays the groundwork for characters we care about.

Three people sharing time in a cabin might not seem like an exciting setup for a movie, unless, of course, there’s some supernatural presence murdering them in grisly fashion. However, when you lock away three great actors who know their characters inside out, a smart script that allows them the space to develop but pushes the movie forward scene-by-scene, and direction that feels seamless with the storytelling, then you have something special, and that something special is Your Sister’s Sister. While I think Shelton’s previous film had more at play concerning male relationships and sexual politics, this one, with a more straightforward, farcical plotline, is still plenty entertaining and with strong character work (the ending does leave one very large question unanswered). This is charming, sweet, unassuming little indie film that will provide a solid dose of smiles and laughs.

Nate’s Grade: B+