After undergoing a cosmetic facial surgery, a mother, portrayed by Susanne Wuest, returns to her contemporary and isolated lakeside home, accompanied by her ten-year-old twin sons, Elias and Lukas. With her face obscured by bandages, revealing only her eyes and mouth, the twins are immediately distressed by her altered appearance. What amplifies their unease is her bizarre behavior; she seems to deliberately ignore Lukas while conversing solely with Elias. In spite of it being midsummer, she enforces strict rules, demanding that the blinds remain shut during daylight hours and insisting on an oppressive silence within the household while allowing the boys some freedom outdoors.
Moreover, her demeanor turns harsh when she physically punishes Elias for minor acts of mischief or disobedience, a startling contrast to their mother's previous gentle nature. As the twins grow increasingly suspicious, they start to question whether the woman behind the bandages is genuinely their mother. Their fears are validated when they come across an old photograph featuring their mother alongside a mysterious woman who bears an unsettling resemblance to her, both dressed in matching outfits.
Convinced that they are harboring an impostor, the twins resolve to confront her. They bind her to a bed, resorting to torture methods in an attempt to extract the truth from her, silencing her cries for help by sealing her mouth with tape. Just as the tension escalates, two staff members from the Red Cross arrive, intending to collect donations. They wait patiently for the mother's return, but their patience wanes when Elias stealthily pilfers a substantial amount of cash from his mother’s purse and offers it to one of the employees.
At this point, the mysterious woman manages to free herself from the tape and calls for aid, but her cries go unheard. The twins, determined to restrict her ability to call out for help, resort to using Super Glue to seal her lips shut. However, they later realize that they have gone too far when she struggles to eat, prompting them to cut her lips open with scissors.
As desperation mounts, and after a series of disturbing events culminate with her urinating in bed, the twins briefly allow her the freedom to use the restroom. This moment of leniency backfires as the woman takes advantage of the opportunity to overpower them and attempt to flee. Yet, the twins have anticipated this and set a booby trap that charts her back to unconsciousness. When she regains consciousness, she finds herself glued to the living room floor, facing a terrifying predicament.
In a shocking twist, Elias contemplates igniting the house to force the woman to unveil the truth, yet she staunchly claims to be their real mother. In a heart-wrenching turn of events, she reveals a painful secret: Lukas died in an accident prior to these harrowing events, leading Elias to hallucinate his brother's presence. Tearfully, she reassures Elias, revealing that Lukas’s tragic fate was not his responsibility and imploring him to release her so they can both find closure.
Elias, still clinging to the belief that a real mother's insight would enable her to see Lukas, questions her about his brother’s whereabouts. Unable to perceive the vision of Lukas who threatens to ignite a curtain, she cannot provide an answer. In a moment of madness, Elias, convinced that he must act, lights the curtain aflame, leading to catastrophic consequences. The mother tragically perishes in the flames before help can arrive, leaving behind haunting memories of love entwined with loss. The film culminates in a ghostly image of the mother united with her sons in a sprawling cornfield, a poignant symbol of their everlasting bond amidst the tragedy.
