The film is set shortly before Christmas in the North Country of Upstate New York, near the Akwesasne ('Where the Partridge Drums') St. Regis Mohawk Reservation and the border crossing to Cornwall, Ontario. Ray Eddy (Melissa Leo) is a discount store clerk struggling to raise two sons with her husband, a compulsive gambler who has disappeared with the funds she had earmarked to finance the purchase of a double-wide mobile home. While searching for him, she encounters Lila Littlewolf (Misty Upham), a Mohawk bingo-parlor employee who is driving his car, which she claims she found abandoned with the keys in the ignition at the local bus station. The two women, who have both fallen on hard economic times, form a desperate and uneasy alliance and begin trafficking illegal immigrants from Canada into the United States across the frozen St. Lawrence River for $1,200 each.
Ray's older son T.J. wants to find a job and help support the family so they can afford to eat something more substantial than popcorn and Tang. He and his mother clash over whether he should remain in high-school and look after his little brother Ricky or drop out to work. To make matters worse, T.J. sets an outside corner of the trailer afire with a torch in an attempt to unfreeze the water pipe. Lila longs for the day she will be able to reclaim and live with her young son, who was taken from her by her mother-in-law immediately after his birth.
Because the women's route takes them from an Indian reservation in the US to an Indian reserve in Canada, they hope to avoid detection by local law-enforcement. However, their problems escalate when they are asked to smuggle a Pakistani couple and Ray, fearful their duffel bag might contain explosives, leaves it behind in sub-freezing temperatures, only to discover it contained their infant baby when they arrive at their destination. She and Lila retrace their route and find the bag and the baby, which Lila insists is dead, but which she revives moments before being reunited with the baby's parents. The experience leaves her shaken, and she announces she no longer wants to participate in the smuggling operation. But Ray, needing just one more crossing to finance the down payment on her mobile home, coerces her into joining her for one last journey.
They pick up two Asian women from a strip club for crossing. When the club owner tries to shoot them, Ray successfully threatens him with a gun. When she is re-entering her car, the irate club owner retaliates by shooting Ray in the ear. Shaken, her fast and erratic driving catches the attention of the provincial police. Ray tries to elude capture by crossing the frozen river where one of the wheels of the car breaks through the ice. The four women abandon the vehicle and take refuge at the Indian reservation.
Because the police are demanding a scapegoat, the tribal head decides to excommunicate Lila for five years due to her smuggling history which involved the death of her Mohawk husband. Surprised then saddened by the news, Lila gives in to Ray's pleas to go free for the sake of her children. However, running through the woods, Ray has a fit of conscience and returns. She gives her share of money to Lila with instructions for taking care of her sons and seeing through purchase plans for a trailer home. She and the illegal immigrants are surrendered to the police and a trooper speculates she will have to serve four months in jail. She calls her son T.J. to explain what has happened.
Lila pushes her way into her mother-in-law's home and reclaims her infant son. She and the baby show up at the Eddy trailer while T.J. is still on the phone with his jailed mother. In a day scene, T.J. completes the welding of a bicycle-propelled carousel bearing his younger brother and Lila's strapped in baby. He pedals the carousel while Lila smiles on. A truck nears carrying the new trailer home.
Output: Why does T.J.set the trailer on fire?