In the summer of 1976, Alice and Tom Bell, a married couple from Seattle, set out on a cross-country road trip in their new Winnebago, heading east through Canada toward the Montreal Olympics. Alice, a 36-year-old former school secretary, and Tom, a high school football coach, are seeking reprieve from grief: Their baby son was stillborn the previous year, and Alice has been struggling with guilt and emotional withdrawal.
At a campground in Hope, British Columbia, Alice meets a young hitchhiking couple. The girl, who introduces herself as Ocean, is about five months pregnant. Her boyfriend calls himself Blue. Tom invites them to camp at their site for safety after a group of rough-looking bikers arrives nearby. Over dinner, the couple reveals they have no family. Alice is unsettled by the girl's pregnancy but agrees to let them stay.
The narrative shifts to reveal that the young woman is actually Jenny Perron and her boyfriend is Simon Gray. They are fugitives from White Cliff who fled by stealing a boat and traveling at night. Simon suggests stealing from Alice and Tom, but Jenny refuses, insisting no one else get hurt.
Tom agrees to drive them farther east. Simon secretly steals cash and a hunting knife from one of the bikers' saddlebags. At a rest stop, Alice overhears a radio report describing two suspects wanted in connection with a homicide, but she talks herself out of believing the descriptions match the couple.
At a store near Kamloops, Alice finds a newspaper identifying the couple as Simon Gray and Jenny Perron, wanted for the stabbing murders of Jenny's mother, Isabelle Larson, and stepfather, Robert Larson. Alice tears out the article and waits until evening to show Tom, unable to find a pay phone.
Tom loads his handgun, and they try to sneak out while the couple sleeps. Simon hears them and confronts them. Alice accidentally calls the girl "Jenny," revealing she knows their identities. Tom draws the gun, but Alice stumbles into him, knocking his aim aside. Simon tackles Tom, breaks his collarbone, and recovers the gun. He ties Alice and Tom to the bed, announcing Alice will drive in the morning.
Simon now controls the group through force. He takes their money and weapons and orders Alice to drive eastward. When the biker from the campground pursues the RV demanding his stolen property, Simon takes the wheel and runs the man over, killing him, then forces Alice to help hide the body.
The RV's radiator cracks, forcing a stop. Simon and Jenny dye and cut their hair to alter their appearance. Simon forces Alice to help rob a gas station. When Jenny begins bleeding, Alice insists on taking her to a doctor. While Jenny is behind an exam curtain, Alice writes a note identifying the fugitives and stating she and Tom are hostages. The doctor confirms the baby is healthy, but Jenny discovers the note before they leave and tears it to shreds outside, telling Alice she will not inform Simon but making clear the escape attempt has failed.
Simon's violence escalates. During a Dairy Queen robbery, he pistol-whips a teenage worker and threatens him with a deep fryer. Alice throws a cleaning cloth at Simon to stop the beating and later deliberately lurches the RV to spill his milkshake on him. At a church in Cranbrook, Simon savagely beats a church leader named Phoenix who apparently recognizes him from news reports. Alice is struck when she tries to intervene.
The RV gets stuck near Fernie, and an elderly farm couple, Ruth and William Polanski, tow them out. Simon repays their kindness by pulling his gun, confiscating their firearms, and forcing everyone into the farmhouse basement. He and Jenny take over the house while Simon repairs the Polanskis' truck.
During their captivity, Alice and Tom share honest conversations about their marriage and grief. Jenny grows increasingly troubled by Simon's violence, reflecting on her past: her controlling mother, her father's death when she was 11, and the day Simon first showed her kindness when no one else would.
When a local constable arrives to check on the Polanskis, Simon opens fire, wounding the officer. He forces Alice to drive the repaired truck through the garage door, and they escape under gunfire. The truck breaks down in Alberta, and they walk miles along railroad tracks to a motel in Blairmore. That night, Jenny secretly calls police to report people trapped in the basement, then hangs up in a panic. Simon discovers she left the room and confronts her, but Jenny lies, saying the call did not connect.
Simon robs a jewelry salesman at the motel and forces Alice to drive the stolen car east. On a dirt road, Alice strikes Simon with a tree limb and sprints onto a wooden trestle bridge spanning a deep ravine. Simon pursues and shoots her in the calf. As he advances with the gun raised, Jenny pleads with him to let Alice go. Simon refuses, insisting they cannot leave a witness. Jenny declares she will never forgive him if he kills Alice. When Simon raises the gun again, Jenny shoves him off the guardless edge. He falls into the ravine and dies.
Alice returns to Jenny, who is holding the gun to her own temple. Alice talks her down by invoking her unborn baby, sharing that her own son died during labor and she would have traded places with him. Jenny releases the gun.
Jenny confesses the full truth. The baby is not Simon's; her stepfather, Robert, sexually assaulted her repeatedly beginning when she was 15. Her mother knew Robert had abused other girls at their dance studio but did nothing. When Jenny became pregnant, her mother blamed her and threw her out. Simon took Jenny in and accepted the baby as his own. Jenny describes the night of the murders: She went to the house to ask Robert for money. Her mother returned, realized Robert's predatory behavior had continued, and turned her fury on Jenny rather than Robert, slapping her and calling her a whore. Jenny grabbed a knife and stabbed her mother, then pursued Robert and killed him. Simon helped her flee.
Alice and Jenny drive to a hospital in Blairmore, where police arrest them at gunpoint. Jenny pleads guilty to second-degree murder and is sentenced to the Prison for Women in Kingston, Ontario, eligible for parole in 15 years. She gives birth in prison, holds her daughter briefly, and writes a letter asking Alice and Tom to adopt the baby, requesting that the records be sealed and the child never learn about Jenny or the circumstances of her conception.
In September 1976, Alice and Tom read the letter in Seattle. That night, Alice drags the baby crib from the basement and places it in the empty room, knowing the child is their daughter. In an epilogue set in August 1991, Jenny, released on parole, takes a bus to Seattle. She watches from a distance as Alice and a nearly 15-year-old girl named Katie walk to a beach with a small white dog. Jenny does not approach. After they leave, she walks to the spot where they spread their blanket and lies in the warm sand, smiling. Her daughter is happy and loved.