Thirteen-year-old Becky Hooper is under scrutiny as she responds to investigators about a recent incident at her family's home. Her responses are vague, revealing little as she struggles with memories of the event. Two weeks prior, Becky, a high school student facing bullying, is grappling with the loss of her mother from a year ago. The tension in her relationship with her father, Jeff, is palpable as he attempts to mend their bond through a trip to their lakefront home.
In the meantime, Dominick, a Neo-Nazi inmate portrayed by Kevin James, is being transported alongside his associates Apex, Cole, and Hammond. In a ruthless act, Dominick orchestrates a guard's death to escape, beginning a horrifying spree that sees them hijacking a family's car, likely killing the occupants in the process.
At their lake house, Jeff is joined by his girlfriend Kayla and her young son, which sends Becky into a tailspin of anger and hurt when Jeff reveals their engagement. Feeling abandoned, she flees the scene with her loyal dog, Diego, eventually returning to her secret fort in the woods, where she retrieves a unique key in the shape of a valknut symbol.
When Dominick and his gang arrive at the house, they quickly take everyone hostage and demand the key. Amid the chaos, Kayla and Ty attempt to escape but are thwarted by Apex. While Jeff tries to protect Becky by lying about her whereabouts, Dominick inflicts pain on him to extract the truth, shooting Kayla in the process.
Becky, hidden in the woods, engages with her father over a walkie-talkie, claiming she's called the authorities. Dominick, however, calls her bluff and brings Jeff to confront her. As Dominick tortures Jeff, Becky, feeling cornered, agrees to hand over the key, but Jeff urges her to flee for her safety. In a tragic turn, Becky watches as Dominick kills Jeff after he expresses his love for her.
In a fierce moment of survival, Becky confronts Dominick, gouging out his left eye with the key before escaping with Diego. As Dominick returns to the house for revenge, Cole hunts Becky down, but she cleverly defends herself, killing him with a series of well-placed attacks using her school supplies.
Apex, showing unexpected kindness, tries to protect Kayla and Ty while Dominick pushes him to declare his loyalty. After discovering Cole’s lifeless body, Hammond pursues Becky to the lake, but she outsmarts him with fatal consequences. In a final showdown with Dominick, Becky orchestrates a brilliant ruse to lure him away, leading her to run over his head with a lawnmower.
Despite the carnage, the tale takes a dark twist as Becky ultimately shoots Apex before being joined by Kayla, Ty, and Diego, awaiting the police. Presently, as Becky sits coolly denying any involvement in the murders, her demeanor reveals a chilling change—the innocent girl seemingly gone, replaced by a predator.
