The film kicks off with young lovers turned criminals, Mickey (Bill Skarsgård) and Jules (Maika Monroe), as they attempt to rob a gas station. Their plan quickly unravels when Mickey inadvertently causes the cashier to faint, leaving him unable to open the register. In a moment of improvisation, Jules hands him a snack to facilitate the register's opening, allowing them to escape with cash and their unexpected treat.
Desperate to flee the authorities and their mundane lives, the couple sets off for Florida. However, their excitement wanes when they discover their car runs out of gas, leading to the irony of being stranded after robbing a gas station. Determined not to be deterred, Mickey and Jules decide to leave their vehicle behind and search for another way forward, soon stumbling upon an inviting house.
They attempt to break in, but upon discovering the front door is dead-bolted, they turn to a crowbar that Jules conveniently provides. Once inside, the duo tries to get comfortable while plotting their next move. The allure of cocaine leads Mickey to hatch a scheme to siphon gas from the homeowners' vehicle, but their invasion takes a dark turn when they discover a little girl named Sweetiepie (Blake Baumgartner) chained in the basement.
Although Jules feels compassion for the girl and wishes to help, Mickey is hesitant at first. Ultimately, he gives in to Jules' insistence, and they rush back upstairs only to confront the seemingly amicable homeowners, George (Jeffrey Donovan) and Gloria (Kyra Sedgwick). Mickey, adrenaline-fueled, holds George at gunpoint. Nevertheless, George attempts to de-escalate the situation by offering them the chance to leave with whatever they have taken but makes it clear that they won't leave without Sweetiepie.
Reluctantly, George leads them back to the basement, where he releases Sweetiepie. However, chaos ensues when Sweetiepie bites Mickey, prompting George to headbutt him unconscious. Upon regaining consciousness, Mickey finds himself bound to a bed. Gloria attempts a seduction that turns increasingly bizarre, playing into her disturbing mommy fantasy and showing Mickey images of her imaginary son, whom she claims is named “Ethan.” Meanwhile, Jules is trapped in the basement, attempting to converse with Sweetiepie, who remains silent and unresponsive.
The unsettling ordeal stretches on for days, revealing the twisted dynamics at play. Jules reveals her painful past of being abandoned, but the tension escalates when Mickey appears to fall for Gloria's advances until he plots an escape. With ingenuity, he seeks to use Jules' tongue stud to frees himself. After a painful extraction, the duo manages a temporary escape plan, only for George to intervene, threatening to maim Mickey if he doesn’t divulge Jules' whereabouts.
Just as tensions simmer, Jules surprises everyone with her own plan, revealing "Ethan" to be a mere porcelain doll, a clear sign of Gloria's madness. A frantic standoff leads to chaos when George and Gloria attempt to restrain Mickey and Jules during an ill-fated dinner, unveiling their sinister intentions to overdose them on heroin, disguising it as a junkie accident.
Just when hope seems lost, a police officer arrives, having linked their abandoned vehicle with the robbery. George desperately attempts to deflect suspicion while stalling for time. Meanwhile, Jules devises an escape plan, rousing herself with cocaine. They manage to deceive George and Gloria into thinking they have fled, only to reemerge in a final confrontation.
As the climactic showdown unravels, Mickey and Jules struggle against George's gunfire. Mickey professes his love for Jules in a heart-wrenching moment right before he makes a desperate move to escape, sacrificing himself to save her. The scene turns tragic as Sweetiepie rises against the monstrous couple, taking justice into her own small hands by shooting George.
With freedom finally within reach, a deranged Gloria wanders outside only to witness her husband’s lifeless body. Rather than succumb to her loss, she clings to her delusions. However, Sweetiepie finally breaks her silence, offering to go with Jules, and together, they embark on a new journey towards a hopeful future.
The film concludes with a heartwarming yet bittersweet home video capturing Jules and Sweetiepie joyfully playing at a Florida beach, now aspiring business owners of a small knick-knack shop named after Mickey, encapsulating both the darkness they escaped and the new life they have forged ahead.
