"Frozen River," a story of abject desperation, feels so real and immediate that it plays almost like a documentary.

That's much to the credit of first-time writer and director Courtney Hunt, as well as Melissa Leo and Misty Upham as two women who make what seem like poor choices to keep their families together. It's a moving and powerful film, heartbreaking and intense.

It's also a look inside what the poorest of American families face. Struggling to get by, where do they turn if things get worse?

Leo plays Ray Eddy, a suddenly single mom living in a broken-down trailer in frozen upstate New York. Her husband, a gambling addict, has run off with the down payment on a double-wide trailer, the family's long-held dream. Ray's job as a part-time clerk at a discount store won't make ends meet; she feeds her sons dinners of Tang and popcorn between paychecks.

Circumstance leads her to cross paths, unhappily, with Lila (Upham), a member of the Mohawk tribe who has plenty of troubles of her own. Lila's husband is dead, her mother-in-law has stolen her 1-year-old son and she works at a tribal bingo hall, but poor eyesight prevents her from accurately counting money, among other things.

But Lila has another means of employment of sorts: She smuggles illegal immigrants across an unguarded segment of the border between the United States and Canada. In fact, it's a frozen chunk of river (thus the title), where the ice is thick enough to drive across. Lila's been caught before, so she needs a driver. (The local car dealers won't sell her anything with a trunk.) That's where Ray comes in.

Ray doesn't want to do it. In more normal circumstances, she might be filled with self-loathing over such a choice. Yet Leo's performance makes it clear that Ray is way past the luxury of that sort of emotion. She simply sees no other alternative. Lila is in much the same boat.

Leo's performance is astounding. When we first see her, the camera slowly reveals her, weathered, worn and crying. There are miles on Ray's face. Upham is also quite good. Like Ray, she just plugs away each day, struggling to stay above water.

Also of note are the performances of Charlie McDermott and James Reilly as Ray's sons. Reilly plays Ricky, a boy who doesn't understand what's going on in his family's life. He has the unquenchable optimism of the very young; whenever someone knocks at the door, he responds, "Dad?" and your heart breaks.

McDermott plays T.J., 15, forced to grow up too fast. Frustrated and confused, he's not really sure how to respond.

It's for them and for Lila's son that the women are risking so much for so little ($600 per person smuggled). While it's not an uplifting film, and its politics are strictly personal, "Frozen River" at least illuminates a sort of striving that, if not exactly heroic, is at least, in its way, noble. And there's a certain rugged beauty in that.