Filmmaker Lynn Shelton made her name as a mumblecore mainstay with movies like 2009′s Humpday—which, like many of her films, was made in the Pacific Northwest with a small cast and a heavy reliance on improvisation. Her latest movie in that mold is Your Sister’s Sister, in theaters Friday, starring Emily Blunt and Rosemarie DeWitt as half-sisters, with Mark Duplass as Blunt’s best friend. DeWitt and Duplass each retreat to an island cabin, after a bad break-up and a brother’s death, respectively. Instead of finding some alone time, all three collide. Shelton spoke to TIME about her creative process and the benefits of collaboration.
How much of Your Sister’s Sister ended up being improvised?
With Humpday, it was just an outline, and 100% of the dialogue was improvised. But in this case—because Emily and Rose had not done it before much, and they were already terrified as it was—I wanted to give it sort of a safety net. Most of the scenes were written out but only somewhere between 20 and 30% of what you see on screen is as-written.
Given that there were some last-minute cast changes [Rosemarie Dewitt stepping in for Rachel Weisz] and that it was a pretty quick shoot, how did you go about establishing the trust necessary for that working style?
You just cast the right people who are willing to really bare their souls to each other and create instant intimacy. Rosemarie came two-and-a-half days before the shoot began, and luckily the very first part that we shot was between her character and Mark Duplass’ character, Jack, who in the movie have never met. So that was perfect. And then the most amazing thing was that instant chemistry that she was able to create with Emily, as sisters. We were all staying in this beautiful piece of property, in houses just a stone’s throw away from the house we were actually shooting in. We’d bunk together, we’d eat lunch and dinner together at this beautiful lodge, and then we’d walk back over to our workplace. They threw themselves into it and very open-heartedly just dove in.
Were there any particularly great moments that weren’t in the script?
The opening scene, this memorial service with Mike Birbiglia and Mark [Duplass], all of that material they came up with—the content of the stories they told about the dead guy. And when Jack and Hannah [Rosemarie DeWitt's character] are getting to know each other that first night in the cabin and drinking tequila—probably one of my favorite scenes—with Jack just kind of waxing poetic about Hannah’s butt. Then there’s a story that Hannah tells that made Emily blush for real on screen. All I said to Rose was that we need to think of something that’s going to really embarrass Iris, and I whispered that into her ear and she was like “I got something.” She didn’t even tell me what she was going to say. That’s the beauty of improv. You can surprise people and get genuine reactions.
The cast members are listed in the credits as “creative consultants.” Is improvisation what earned them that title?
That and also they’re involved in the development process. It invests the actors more in the process and it allows them to find a lot of overlap between themselves and the character, so that really they can just slip that character on like a hand into a glove. It’s also extremely helpful to have a lot of backstory worked out as a foundation, so that once you get into a room and somebody lobs a line at you, you know exactly who you are, what you are to each other and what’s happened between you two up to the moment of the scene. What comes out of your mouth is just going to be second nature. If you don’t have that foundation, you’re just floundering. I really want to make sure they got credit for all that.
If the process helps the actors find themselves in the characters, is there also any of you in there?
I don’t think I can help but bring myself to the characters, because I’m the final arbiter of what ends up on the page and what ends up on the screen. I have very uncomplicated relationships with my sister and my brothers. I’ve observed, though, really fascinating and deep and textured sibling relationships, all my life, around me. We drew on those second-hand stories I had and also stories from the lives and from observations of the actors, which is another great aspect of collaboration. You’re getting more meat for the stew.
You also recently directed episodes of New Girl and Mad Men—that must be a very different work environment. How do you bring your own style as a director to something so different from the films you make?
My strengths are working with actors and having a good ear and eye for naturalism, what sounds authentic, and really getting in there with the actors to find the scene. I’m not expecting to go in and turn a word-perfect, script-oriented show like Mad Men into one of my improvised works; I’m there to fulfill the creator’s vision and so I’m the captain of the ship but I’m not the admiral of the fleet. It’s kind of liberating.
And New Girl is a very female-centric show. Do you think the environment for female creatives in movies and TV is improving?
I don’t really have a macrocosmic view of that. I do read articles about how there were no female directors at Cannes, and in general I know there’s kind of a dearth, but right now it seems like there’s actually some good shows that are getting attention. Liz Meriwether with New Girl and Lena Dunham from Girls are a couple of nice examples. I think that a good idea and a good show is a good idea and a good show, so hopefully we’ll keep going in this direction and those will just be the pioneers. We’ll have more shows like that, that show different points of view and more diversity on screen—real diversity, diversity in a way that we haven’t seen before.
Not to give anything away, but there are a few mysteries in Your Sister’s Sister that you leave the audience to wonder about. Do you have a take on how much should be left to the imagination in a film?
Absolutely. We have backstory up the wazoo but I don’t want to give it all. Real people don’t do that, they don’t say ‘remember the time we blah blah blah…’ because that’s not how life works. I don’t want to see it on screen because it just rings so false. And I don’t like packages too perfectly wound up at the end of a movie. I’d rather the choose-your-own adventure ending.
Shelton just wrapped her latest movie, Touchy Feely. Starring Rosemarie DeWitt, Josh Pais, Ellen Page, Allison Janney, Scoot McNairy and Ron Livingston, it is her first film with an ensemble cast.