By ANGELA DAWSON

Front Row Features

HOLLYWOOD—Lynn Shelton had never stepped onto a movie set when she made her features film, “We Go Way Back,” in 2006.  She found herself introducing herself to her crew. “Oh, hi. You’re the gaffer? What do you do?” she recalls innocently asking.

From that inauspicious beginning, the Seattle-born filmmaker has quickly figured the moviemaking process out. She made the indie darling “Humpday,” in 2009, helmed an episode of “Mad Men” and she has now written and directed her fourth feature, “Your Sister’s Sister,” a romantic comedy starring “The Devil Wears Prada’s” Emily Blunt and “The League’s” Mark Duplass.

Shelton’s latest feature may be her most commercial to date. It’s about an aimless young man (Duplass) who accepts an offer from his platonic best friend (Blunt) to work out his issues over his brother’s death at an isolated family cabin on an island off coastal Washington for a weekend. The cabin turns out to be not so isolated after all. His friend’s sister (“United States of Tara’s” Rosemarie DeWitt) has taken up residence there to get over a recent breakup with her longtime girlfriend.  While commiserating over drinks, the duo becomes intimately acquainted, only to be surprised the following morning with the arrival of their mutual host. Complications ensue.

Shelton wrote the outline of the script based on an idea presented to her by Duplass, best known for co-writing and directing the comedies “Cyrus” and “Jeff, Who Lives at Home.” The actors themselves improvised most of the dialogue. Blunt, who plays sweet-natured Iris in the low-budget film, says it was a fun experience as an actor.

“I signed on for the experience really,” she says. “I felt I could stretch my limbs on it. It was challenging and exciting and we all took a leap of faith with it. It turned out to be pretty good.”

Even a last minute casting change—DeWitt stepped in just days before production started when British actress Rachel Weisz dropped out owing to a scheduling problem—didn’t faze the emerging filmmaker. She simply turned to DeWitt, whom she’d known from “Mad Men.”

Front Row Features: Can you talk about casting Emily Blunt and the decision to have her speak with her native British accent?

Shelton: It’s improvisation. I didn’t want anyone to have to worry about faking an accent and improvising at the same time. I wanted it to be as natural and organic as possible. The half-sister paradigm worked great so it didn’t matter if one was American and one was English. The original actress (Weisz) we cast as her sister was British as well.

Front Row Features: How did the casting change work out for you?

Shelton: I like it better that one’s American and one’s English because they were never supposed to be full sisters anyway. Emily told me it was an easy “yes” after hearing my initial pitch to her. Her agent was a fan of “Humpday,” so he liked the idea of her working with me. She had just worked on a whole bunch of big movies and so I think it was good timing to call up and say, “Look, spend a couple of weeks with us. It’ll feel like film camp. It won’t even feel like you’re making a film. I guarantee you’ll have a fabulous time and you’ll have home-cooked meals and it will be a wonderful experience.”

Front Row Features:  Do you feel lucky to have found someone of Emily’s stature in Hollywood to be in your low-budget independent movie?

Shelton: Yes. She really did it for the experience because it was so different. She’d had a fond memory of working on her first feature, “My Summer of Love,” which also was improvised, and never thought she’s have a chance to work that way again, so it was another reason.

Front Row Features: How did this story come to you?

Shelton: Mark came to me with a kernel of an idea. Emily was at the top of my list, and when we lost (Weisz) for Hannah, Rosemarie was it. I was terrified this movie was dead in the water three days before the production without one of our leads. As soon as I thought of Rosemarie, I thought everything’s going to be OK. Luckily, she was able to do it even though she already was on a TV show, and she had to squeeze (filming “Your Sister’s Sister”) around that.  It wasn’t like replacing anybody in any kind of movie; it was a very specific kind of paradigm. So when I brought up her name to Mark (Duplass) he said, “I think she’ll say yes if she’s available.” She had told him a year earlier she had seen “Humpday” (in which he starred) and wanted to work with us.  Not everybody wants to improvise because it’s tough and a very different way of working than a scripted movie.

Front Row Features: Why was Emily at the top of your casting list?

Shelton: I had been obsessed with her ever since I saw her in “Sunshine Cleaning,” and not recognizing her from “The Devil Wears Prada.” I literally walked out of the theater and wondered, “Who is that young American actress I’ve never seen before?” And then I looked her up on IMDB and thought, that’s mind-blowing. Every one of her very disparate kinds of roles that she’s played, I totally believe.

Front Row Features: What does Rosemarie bring to the role of Hannah?

Shelton: She’s so emotionally grounded and so credible in every role. She’s such a charmer. The thing I like about her in my film is that she’s able to bring so much of her own cadence and her own personality to the fore because she’s one of the funniest most charming people I’ve ever met. It was great to let that shine through.

Front Row Features: The ending is open for interpretation by the viewer. Did you purposely want to leave it uncertain for the viewer to guess what happens next?

Shelton: The plan was always to have the ending that’s in the movie. Just in case, we shot a couple of different endings. I had a series of rough-edit screens and at the very first one, it was unanimous, the ending we had was the right one.

Front Row Features: Who’s your biggest creative influence?

Shelton: Woody Allen. The idea you could make a feature film with conversation as the base—natural, human conversations—that was an enormous influence for me. My mom was a French New Wave fan, so (Francois Truffaut’s) “Jules and Jim” was a big influence on me as well and Jean-Luc Godard.

Front Row Features: What’s your next project?

Shelton: I just shot my fifth feature called “Touchy Feely” with Rosemarie DeWitt. We wrapped about three weeks ago. I wrote the role for her. I’ve also made a couple of web series along the way, music videos and so on.