On a bitter morning in early April, on the south shore of Flathead Lake in northwestern Montana, Vera Brunner-Sung stood still behind a camera. At first, all was quiet. Then came the hollow knocking of an actress' boots on the dock, and seagulls crying, and water lapping at the trestles. Suddenly, everything seemed quite loud: A nail gun; a truck in reverse; a plane overhead. "Cut," Brunner-Sung called. She wore stiff jeans, leather boots with cowboy heels and an old blue coat. Thick dark hair topped her lanky frame. "I liked that," she said. "Let's move on."

The film, Bella Vista, is Brunner-Sung's first fictional work, built from trappings of her own life. It is less a story than a threading together of images and ideas that say something – "something small," she insists – about finding oneself at home in the West. Doris, played by Kathleen Wise, is in her early 30s. After years abroad, she comes to Missoula, Mont., to teach English to international students at the university. A fiercely quiet woman, her long hair often pulled back, she spends much of the film walking through the camera's wide, fixed frames. She seldom speaks, except with her students, who, at first, seem similarly out of place. "Doris is not someone we're supposed to get to know that well," says Brunner-Sung. She is a passerby, lost in her transient anonymity. It is never clear whether she intends to make Missoula her home. If there is a question that undergirds the film, it is, says Brunner-Sung, "Do I stay, or do I go?"

Brunner-Sung, 34, moved to Missoula from Los Angeles in December 2011. Her fiancé had been hired as an archivist at the University of Montana, and she took a teaching position in the film department. Missoula was the smallest city she had lived in. She found herself telling cashiers, unasked, that she was new: "I was really excited about being a stranger." She learned the city by walking through it: Down Catlin to Third, where she watched kids ride four-wheelers around a parking lot; up Mount Sentinel, from which the valley's sprawling lights reminded her of L.A. She loved these walks as she loves slow, avant-garde film – "I like to stop and take a breath and let my eyes wander" – and came to know Missoula at a studied distance: The apartments crammed into back alleys, the tracks bisecting town diagonally, the clapboard houses tilted on their foundations. She scribbled her observations onto note cards. Eventually, these moments became scenes, and the person who walked through them became Doris. By the following September, Brunner-Sung had written a script.

I met her in April, in Polson, Mont., on one of her last days shooting. We spent the morning with the crew at the Bayview Inn, all crammed into the bathroom of Room 17 while she filmed Wise shifting restlessly in bed. This, I thought – the stiff sheets, the carpet, the cigarette smoke drifting under the door – was the nadir of lonely transience. "Do you still see yourself in Doris?" I asked Brunner-Sung later, as we drove south for another scene. "I don't feel as lost as Doris does," she said. "I think she looks around Montana and doesn't see herself here."

The anonymity Brunner-Sung once relished had worn off; she now recognized people in the grocery store. "I think if you decide to open yourself up to a place and make it your home, the place becomes you." So would she stay in Montana a while? "I don't plan on growing old here," she said.

Brunner-Sung spent her first 18 years in a house on Longshore Drive in Ann Arbor, Mich. Her father had emigrated from Korea, her mother from Switzerland. Of mixed race, she understood what it meant to be "between things"; to her, borders – geographic, ethnic – seemed mutable. She saw her parents as converts to the American mythology that anything was possible, and that their coming to the States was a chance to redefine themselves.

When Brunner-Sung was in college, the house on Longshore, a 1940s single-family home with creaky floors and a single-car garage, burned down. The structure her parents built in its place was tall, blockish and set at a different angle in the yard. Eventually, Brunner-Sung returned to Ann Arbor, but felt like a stranger in the new house. She missed the staircase and the sound of the second-floor fan they used when summers got too hot. She thought about memories and the meanings that people attach to material things.