Frozen River is the story of Ray Eddy, an upstate New York trailer mom who is lured into the world of illegal immigrant smuggling when she meets a Mohawk girl who lives on a reservation that straddles the US-Canadian border. Broke after her husband takes off with the down payment for their new doublewide, Ray relunctantly teams up Lila, a smuggler, and the two begin making runs across the frozen St. Lawrence River carrying illegal Chinese and Pakistani immigrants in the trunk of Ray's Dodge Spirit. At the onset, Ray and Lila's partnership seems doomed to failure as Lila normally doesn't 'work with whites,' but Lila's eagerness to get her baby son back from her mother-in-law who has 'stolen' him, leads Lila and Ray into an uneasy partnership.
At first the money is good and the ice holds. With help from Jimmy. the Mohawk dealer, they make several runs and soon the money for Ray's doublewide is within her grasp. As quickly as things began to go well, the entire scheme is threatened as the home life of each woman threatens to wreck their plan. T.J., Ray's 15 year old son struggles to take care of the house and hold thing together for his younger brother Ricky, while mom is 'at work.' And Bernie, Lila's friend, tries to find her a straight job on the reservation so that she can get out of smuggling and reclaim her baby son. However, Lila, who lives in a camper, feels she has no realistic way to support him without smuggling and rejects Bernie's efforts. Finally, with the money she needs almost set aside, ray and Lila embark on a final run across the river which, if they survive, will set things right. But when the run goes bad, the Quebec police chase the women onto the ice and, with the New York State troopers on the other side of the river, the two women have to make a desperate escape. Trapped on the Reservation, the fate of Lila and Ray is left in the hands of the Tribal Council. With few options left, Ray and Lila's partnership is tested; they must face the consequences of their actions to survive.