Diner waitress and single mother Karla Dyson takes her six-year-old son, Frankie, to a carnival. Once there, Karla leaves her son to take a phone call and hears from her lawyer new information about her current custody battle with her estranged husband. She returns and finds that Frankie is missing and that he left his toy voice recorder behind. Frantically searching for him, Karla spots a woman dragging Frankie into a green Ford Mustang with no license plate driven by a man. As it takes off, Karla tries to stop the car by clinging onto it and drops her phone after failing to do so. Karla then jumps into her minivan and races after the kidnappers.
On a highway, Karla attempts to attract the attention of a motorist. However, her efforts are foiled when the kidnappers throw a tire into the open traffic and cause a pile-up. After the abductors threaten to murder Frankie with a knife, Karla is forced to take an exit ramp before resuming her pursuit.
Karla hears a voice from her son’s toy voice recorder, revealing the female abductor’s name to be Margo. Spotting a police motorcycle, Karla successfully gains the officer’s attention by swaying her car side to side. While the cop orders her to pull over, Karla tries to tell him that her son has been kidnapped, to no avail. The kidnappers notice and ram their car into the motorcycle, killing the officer, before both cars abruptly stop in a field.
After Karla confronts the male driver with no response, Margo approaches her vehicle. Demanding a ransom payment of $10,000 in exchange for Karla’s son, Margo enters the minivan and tells Karla to follow her accomplice’s car. In a tunnel, Margo attacks Karla, who fights back and manages to throw Margo out of the car. Noticing this, the male driver forces Karla to stop tailing him by threatening to drop Frankie onto the highway. After several minutes, Karla spots a traffic jam and finds the Mustang abandoned after having caused a collision; a passerby tells Karla that the pair left on foot.
Karla stops at a police station to report the incident and spots a wall filled with missing posters from the past decade. Fearing that her son will disappear for good if she waits, she promptly leaves. Soon after, she spots the male driver using a stolen black Volvo V70 and chases him until her vehicle runs out of fuel. Attempting to hitch a ride from a fellow motorist, the pair are blindsided when the Volvo rams their vehicle without warning, killing the driver and knocking Karla unconscious.
Waking up, Karla discovers that her son is no longer in the Volvo. As the kidnapper emerges from his car with a sawed-off shotgun, she puts her car into reverse, resulting in the man being fatally struck by a tree. Reading his ID and finding out that his name was Terrence Vickey, Karla decides to travel to his address.
At the Vickey’s house, Karla calls 911 and eventually locates Frankie in a barn with two other kidnapped girls. Promising to come back, Karla and her son run away before being spotted by a distressed Margo with a shotgun, who has learned of her husband’s death. As the pair hide underwater, Margo and her dog locate them. Karla pulls Margo underwater, who wildly fires and kills the dog, and drowns her.
At the barn, Karla is confronted by a man who claims to be Margo’s neighbor. Karla realizes that he is actually participating in the kidnapping ring since he knows how many children were hiding without her telling him. She then knocks him out with a shovel before he can draw his gun. After the police arrive and the children are rescued, it is announced that the events resulted in the dissolution of an international child abduction ring, with Karla being praised as a hero.