FOR HER FIRST FEATURE, writer-director Courtney Hunt traveled just a few hours north of her upstate New York home, to the area where Mohawk reservations line both sides of the U.S.-Canada border. Frozen River was inspired by the real-life operations of smugglers who drive across the iced-over St. Lawrence in winter. The central characters are a middle-aged white woman, Ray (Melissa Leo), and a younger Mohawk one, Lila (Misty Upham). Financially strapped, the two become reluctant partners in smuggling merchandise and people, including — in the film's most harrowing sequence — a Pakistani couple. Both Ray and Lila live in trailers, which makes it a little ironic that Hunt, in town last month to publicize the film, gave interviews at Georgetown's swanky Four Seasons Hotel.

I keep taking pictures of, like, the flowers in the hall, I was in the one in L.A., and I was like, "Let me just snap these orchids."

You made the film initially as a short. How did you expand from the short?

The short takes place in the middle of the storyline. It's when they decide to go back and look for the bag they've left on the ice. I didn't worry too much about keeping that scene in the feature. I just wrote, and thought, "If that scene finds its way back in, great."

I didn't just drop that scene back in. I rewrote it to fit the expanded characters. It happened to be almost the same result. But I almost had to divorce the short to start the feature.

I don't know how I'd react to seeing the feature if I'd already seen the short. That sequence is so powerful in the film.

Luckily, not that many people saw the short. [laughs] In the short, it's more enigmatic. In the feature, it was important that we knew who was who. So I shot the faces of the Pakistani couple. They were the same actors as in the short, but we never saw them. That was one of the mistakes I made. I said, "I'm not doing that again. I'm going to get their faces. I want us to see who it is."

You referred to the couple as "human cargo." It does seem quite a leap to go from goods to illegal immigrants. Did you talk to people in the area about the distinction between those levels of smuggling?

It's funny. I never did. That smuggling culture's been up there since Prohibition. Sometimes it's drugs, sometimes it's alcohol, sometimes it's guns, sometimes it's people, sometimes it's pantyhose. It's whatever is selling. The cigarette tax went down in Canada, and it dried up. Now that tax has gone back up, so cigarettes are back in. There was a period of illegal immigrant smuggling, around the time of 9/11.

Where did you first learn about the smuggling trade through the Mohawk reservations?

My husband's from the area, and everybody up there kind of knows it. Then, through a funny connection, I met a couple of women who smuggled cigarettes. I talked to them, and got a sense of how they did it. They're just normal little businesswomen; they didn't think too much of it.

Most of the Mohawks are not involved in this in any way. But you hear stories about little Mohawk ladies looking out their window and seeing some Chinese guy walking down the street. Or someone in a sari. People on the rez are very much Mohawk. So they'd take note of that.

The film has a lot of small but vivid details, like the desirability to smugglers of a button-release trunk.

I had this friend who was a smuggler, and I talked to him about it. I made it my business to learn, technically, how you pull it off. What kinds of cars work, and who deals in the cars. That's the main implement that you need.

You went to law school, but never practiced law. Yet at one point in your life, you were reading and summarizing transcripts of criminal trials.

It was really helpful. In a trial, somebody's usually lying. You'd have to make that determination. It helped me learn about crime; how rinky-dink it mostly is. Also, I learned the way people actually talk, as opposed to movie dialogue. I hear it all the time, and I can't stand fake-sounding dialogue. My style, if I can have a style after one feature, is more naturalistic.

As the writer of this film, you're crossing a couple of divides. You're going into Mohawk territory, but you're also entering the world of the white working poor, which we don't see very much in films.

Not the stuff of big summer blockbusters. And yet, I think there are people who are doing things that are worthy of movies there as much as anyplace else. I don't like the same-old, same-old. I like people who go unnoticed. "What are they doing? What's their story?" I always have.

Another interesting difference between this film and typical Hollywood fare is the depiction of cars. In the Hollywood movie, the car is liberating. In this movie, the car is imprisoning. They're essential, but they weigh on everyone.

Yeah. My image for this whole movie was that these two women are stuck in a car together. Like her or not, you're with her. You're going to know something about her when you get out of the car, whether you want to or not. To me, it gave some drama to the situation. Not in the classic buddy movie sense, which is hackneyed. My feeling was, if some good dialogue doesn't come out, then they don't talk. I'm good with... nothing.

One thing that brings them together, obviously, is that they're both mothers. Did you include the incident with the Pakistani immigrant mother to underscore that theme?

When the characters came into my mind, they were both moms. I didn't intentionally try to cause that all to happen. I just sort of wrote it as I felt it. It wasn't intentional to make it a mother-themed movie. In the short, people pointed out to me that there was this theme.

You start with Ray, who has two kids, a runaway husband, a job at the dollar store. She's lives in a tiny world, and within 90 minutes she's gone into the reservation, she's met people from Asia. Her world expands very fast, and yet it doesn't seem unrealistic.

I love that too. That because she is on a border, but sort of unaware of it, this whole world opens up to her. I would joke about the whole world coming out of her trunk. This is a woman who wouldn't go out and study other cultures. As Ray goes along, her biases are exposed. And so are Lila's.

The film is set in upstate New York. But do you think of it as sort of a Western?

Yes, I do. In fact, we looked at Westerns. I talked to Melissa Leo about [emulating] John Wayne. I just thought of that beautiful John Ford framing, and that lawless feel, that open frontier. Where are the borders, and who's on what side? You totally have that in upstate New York. There are even pirates up there, that will take your load of cigarettes. I loved that uncertainty. I was completely inspired by that.

(2008, 97 min; opens Aug. 29 at Landmark E Street & Bethesda.)