Around this time, she made her first film. It was a portrait of her neighborhood and the people who lived in it, but she never showed peoples' faces – only their houses and leafy yards, and their voices overlaid on the images. "I wanted to understand what makes up a neighborhood," she said. "It's these structures, but it's also the lives that are lived within them." In 2004, she used the film to apply to the California Institute of the Arts outside of L.A., where she would study under the filmmaker James Benning. In the city, she says, she was struck by how quickly houses were torn down and rebuilt. "I had always thought that 'home' was defined by place – that structures were memory aids, that they provided meaning. But if a structure isn't valued, at least by the economic system, then suddenly architecture isn't permanent. So where does home really exist? In your mind? Is it just an idea? And if so, how do you settle into a place?"

Ten miles south of Polson, we turned west onto a dirt cul-de-sac in the Ninepipe Wildlife Refuge on the Salish-Kootenai Reservation. A father and son were dipping lures into a small murky pond. It was midday, but storm clouds capped the sky so tightly that it felt like evening. The crewmembers pulled stools, tripods, wires and booms from their cars and, within minutes, had trained the camera on a square of marshland. There Sam Sandoval, who plays a Salish man in the film, and whose day job is editing the reservation's Char-Koosta News, would emerge with his tackle box and fishing pole.

Brunner-Sung leaned against a car as she led Sandoval and Wise through their lines. "Now she's going to say, 'Kind of' – like, you're both kind of from here," she explained. The wind flattened the grass and lifted coffee cups off car roofs. Brunner-Sung waited until Sandoval had reached the end of the boardwalk, where the grasses thinned into open water, and then called, "Action on Sam!"

"You visiting from somewhere?" he yelled to Wise.

"Yeah. Kind of."

"Kind of?"

"Well, I mean, I'm living in Missoula right now. But I'm not from here. You?"

"Kind of." The wind carried off his words. A crewmember's knuckles were white from clutching an umbrella.

"Cut!" yelled Brunner-Sung. We ran for the cars.

If Bella Vista is a remark on self-enforced itinerancy, it is also a reminder that everyone, in one way or another, has been displaced. As Doris moves through the film, she encounters people whose definition of home is as complicated as her own: her students; a young boy who lives in a motel with his father; a Japanese man whose gravestone she discovers. The man died in 1945. Later in the film, we learn that thousands of Italian sailors, rounded up from American seas, and Japanese immigrants, removed from their homes, were imprisoned in Missoula at a World War II internment camp. After the war, only Italians, who called Missoula's valley "Bella Vista," chose to stay.

Most disquieting for Doris is her brush with the valley's indigenous history. Of the people she encounters, the Salish fisherman seems most rooted in his home. But even his people, he tells Doris, were forced in 1891 from the Bitterroot Valley south of Missoula onto the reservation where they now live. Since then, they have struggled to preserve their language and culture. "That's sad," she says. "Well," he replies, "when you lose your history, it's dangerous, actually."

It is sad for Doris, Brunner-Sung told me, not just because "she's realizing, 'Even you have been moved from where you're from,' " but also because "she can barely imagine what that would be like, to belong somewhere for so long."

It seems, suddenly, that Doris has no choice in the matter. She is a drifter in a nation of drifters, her presence even more ephemeral beside those who have been there longer and the landscape that predates them all. This is not a conflict of transience and permanence, but of different time scales – the wanderer and the West, the human and the geologic – passing each other by. "There's this mythology of the pioneering spirit that looms over any image of the West," Brunner-Sung told me. "Doris doesn't really have that. It's a false kind of nostalgia, anyway. I wanted to peel back those layers, to show the West as I see it."

But is it the same mythology, perhaps, that keeps Doris moving? "Sometimes I have this delusion when I move that I'll never move again," said Brunner-Sung. "Then, after a while, I start to wonder if I do my best work when I go somewhere else. Is that where inspiration comes from?

"We hold onto this idea that anybody can start over."