Lila Littlewolf (Misty Upham, left) and Ray Eddy (Melissa Leo) smuggle illegal immigrants across the Canadian-U.S. border in Courtney Hunt's film Frozen River. (Jory Sutton/Frozen River Productions/Sony Pictures Classics)

After some opening shots of the steel-gray waterway of the title, the film Frozen River cuts to an even more arresting image: a close-up of actress Melissa Leo‘s face. Haggard, deeply creased and wreathed in cigarette smoke, it’s a map of misery. It’s something rarely seen in contemporary American movies: a relatively average-looking, working-class woman in middle age, unvarnished by make-up and untouched by plastic surgery. In short, a real person.

"Single parents are often driven to desperation. Maybe they don’t drive across a frozen river, but they’ll do something extraordinary to make sure their kid gets into a good school.” — Director Courtney Hunt

Such authenticity is one of the governing principles of Frozen River, the debut feature by Courtney Hunt, herself a middle-aged American woman. The 44-year-old Hunt grew up in Tennessee and came to filmmaking somewhat late in life. She is an inadvertent film buff; when she was a pre-teen, her single mother would drag her to art-house cinemas.

“We went to see whatever was playing,” Hunt says over the phone from her home in upstate New York. “Truffaut, Bergman, Fellini. And Paper Moon and Bonnie and Clyde — that moment in the late ‘70s when Americans seemed to catch on to really good films.”

Frozen River is itself a throwback to that age — the film is character-driven, naturalistic, modest. Melissa Leo (21 Grams, Homicide) plays Ray Eddy, a mother of two who wakes up, just days before Christmas, to find that her husband has vanished — though not before gambling away their final payment on a new, double-wide trailer home. Alone with two young boys who subsist on popcorn and Tang, Ray is unable to make ends meet on her part-time dollar store salary. So she hooks up with a young Mohawk named Lila Littlewolf (Misty Upham), who smuggles illegal immigrants across the Canada-U.S. border.

Director Courtney Hunt on the set of Frozen River. (Jory Sutton/Frozen River Productions/Sony Pictures Classics)

While at Columbia film school, Hunt — who had detoured into law after undergrad — worked with her lawyer husband drafting criminal appeals. Her husband is originally from northern New York and had told his wife tales of the smuggling that went on in the nearby Mohawk reservation. “It was interesting to me,” Hunt says, pointing out that such criminal activity has gone on since at least Prohibition. “It was a real-life adventure.”

Ray Eddy enters this adventure unwillingly, with a handgun constantly at the ready. The manipulative Lila convinces her to drive across the frozen St. Lawrence River, a Mohawk interzone where the border effectively vanishes. There, they pick up a pair of Chinese immigrants who are promptly stuffed into the trunk of Ray’s Dodge Spirit. They speed past a border patrol trooper unmolested. (“He won’t stop you,” Lila says. “You’re white.”) Meanwhile, Ray’s older son, T.J. (Charlie McDermott), gamely tries to assume some share of the family’s burden. When Ray bars him from getting a legitimate job, he secretly participates in a telemarketing scam.

“I don’t think I’m showing anything unusual,” Hunt says. “It’s actually very mundane. Single parents are often driven to desperation. Maybe they don’t drive across a frozen river, but they’ll do something extraordinary to make sure their kid gets into a good school.”

As it turns out, Lila is also a single mom — her infant child is in the care of Lila’s mother, who views her daughter as an unfit parent. Leo, who gives a hard-nosed, ornery and redoubtable performance, is the film’s ostensible star, but Lila is a less familiar character. Upham has the off-kilter charisma of non-professional actor; Hunt cast her after seeing her in a couple of Chris Eyre films. Poor and Native, Lila is consigned to society’s margins even more dramatically than Ray. Consequently, she lives in a cocoon of selfishness as small as the trailer she holes up in on the rez. But self-preservation means possessing, at the very least, a self to preserve. And Lila seems to take a sour, ironic pleasure in sneaking aliens into a country that has made an alien of her.

“The film doesn’t take a point of view,” Hunt says about her portrayal of illegal immigration, “other than to say this is what is going on. But as a nation, the United States is definitely at the beginning of a bigger conversation about the subject. I hope the film can contribute a little bit to that.”

Ray Eddy's trips across the border attract the attention of Trooper Finnerty (Michael O'Keefe) in Frozen River. (Jory Sutton/Frozen River Productions/Sony Pictures Classics)

To the film’s credit and detriment, Hunt never digs too deeply into these themes. Instead, Frozen River gradually accelerates into an action film — albeit a slow-footed, too-calculating one. Ray and Lila speed past the trooper one time too many; Lila’s French-Canadian contact gets cranky; and as soon as the river’s precarious surface is mentioned, you know it’s going to crack.

Up until that point, Frozen River’s earnest tone is as relentless as the forbidding winter weather. And while all that gloom can seem bottomless, the film’s sincerity is unimpeachable. Frozen River won Sundance’s Grand Jury Prize for drama, with juror Quentin Tarantino proclaiming that the film “put my heart in a vise and proceeded to twist that vise until the last frame.”

Hunt’s own heart remains in intimate, small-scale drama. Her next project is a film about an immigrant girl in turn-of-the-century New York. But she cautions that it won’t be nearly as lavish as, say, Martin Scorsese’s The Age of Innocence.

“My favourite part of Frozen River,” Hunt says, “was keeping it small. The world is coming out of Ray Eddy’s trunk — whether she likes it or not. That was my own inside joke about America. I love the idea that the world is coming to us whether we like it or not.”

Frozen River opens in Toronto, Montreal and Vancouver on Aug. 22.

Jason McBride writes about the arts for CBCNews.ca.