The story unfolds in the North Country of Upstate New York, close to the Akwesasne ('Where the Partridge Drum') St. Regis Mohawk Reservation and the Canadian border, just before Christmas. Ray Eddy, portrayed by Melissa Leo, is a hardworking clerk at a discount store, struggling to raise her two sons. Her husband, a compulsive gambler, has vanished with the money she planned to use for buying a double-wide mobile home. While on a quest to locate him, she crosses paths with Lila Littlewolf, played by Misty Upham, a bingo-parlor employee from the Mohawk community who is found driving Ray's husband's abandoned car, keys still in the ignition at the local bus station.
Both women find themselves in dire financial straits and reluctantly team up to smuggle illegal immigrants from Canada into the United States via the frigid St. Lawrence River, charging $1200 per crossing. Meanwhile, Ray's older son, T.J., grapples with the desire to secure a job to help the family escape their dire situation, which consists mostly of popcorn and Tang. This leads to a clash between him and Ray regarding his future—whether he should stay in school to care for his younger brother, Ricky, or drop out to work.
Their situation intensifies when T.J. accidentally sets part of the trailer ablaze in an attempt to thaw out a frozen water pipe. Additionally, Lila yearns for the day when she can reclaim her son, taken from her immediately after birth by her mother-in-law. As they navigate their smuggling route, they attempt to evade local law enforcement by crossing from an Indian reservation in the U.S. to an Indian reserve in Canada.
However, trouble arises as they are asked to smuggle a Pakistani couple. Fearing the possibility of explosives in their duffel bag, Ray leaves it behind in the bitter cold, only to realize that it contained the couple's infant. The discovery endangers them as Lila manages to revive the baby, who Ray was convinced was lifeless. Following this harrowing encounter, Lila expresses her desire to withdraw from the smuggling operation. Yet, Ray, desperate for funds to complete her down payment on the mobile home, persuades her to embark on one last crossing.
Their journey takes a turn when they pick up two Asian women from a strip club. Tensions rise as the club owner attempts to cheat them, prompting Ray to threaten him with a gun. However, during her hasty exit, she is shot in the ear by the enraged owner. The aftermath of the shooting leads to a desperate escape from state police, resulting in Ray’s car breaking through the thin ice of the river. The four women seek refuge at the Indian reservation.
With law enforcement searching for a scapegoat, the tribal leader decides to exile Lila for five years due to her past smuggling activities, which included the death of her Mohawk husband. Heartbroken, Lila eventually heeds Ray's pleas to prioritize her children’s well-being. Yet, overwhelmed by guilt in the woods, Ray turns back. She gives Lila her share of the money, entrusting her with the care of her sons and the plans for their new trailer home. Eventually, she and the illegal immigrants surrender to the police, who speculate that Ray may face four months in jail. In a powerful moment, she reaches out to T.J. to explain her predicament.
In a twist of fate, Lila confronts her mother-in-law and retrieves her infant son. The reunion culminates in a poignant scene at the Eddy trailer, where T.J. constructs a bicycle-powered carousel holding both his younger brother and Lila's baby. As T.J. pedals, Lila watches with a smile, while a truck approaches, carrying their long-awaited new mobile home.
