Jory Sheffield, Jedidiah Goodacre is a gifted fourteen-year-old with a bright future in ballet, following in the footsteps of his mother Cathy Sheffield, Rachael Carpani. His nine-year-old brother Bart Sheffield, Mason Cook, feels overshadowed and often slips into a private world of pretend. Bart carries a dangerous condition—congenital analgesia—that means he cannot feel pain, a reality that puts him at serious risk of injury or infection and compounds his sense of vulnerability.
Cathy Sheffield, Rachael Carpani, is a loving mother who has built a life with her husband Chris. To hide their past, they tell the boys that Chris is Paul’s younger brother. Cathy longs for more children and for a daughter that is truly hers and Chris’s, and she eventually adopts Cindy, the two-year-old daughter of a former dance student who was killed in an accident. Chris, Jason Lewis, slowly embraces Cindy, and Jory sees the addition as a positive, but Bart resents the rival attention that a new sibling brings to the family.
Lonely for attention, Bart becomes acquainted with the elderly next-door neighbor who invites him in for cookies and ice cream and urges him to call her “Grandmother.” Jory later accompanies him and learns that the neighbor is, in fact, Corrine Foxworth Winslow, the grandmother. Corrine’s allure conflicts with Jory’s growing suspicion, and Bart develops an affectionate if secretive bond with her, receiving gifts and being asked to keep their relationship hidden from Cathy. Corrine’s trusted butler, John Amos, Mackenzie Gray, fuels Bart’s fascination with the idea of male power and reveals Corrine’s true identity, while also presenting Bart with a diary that supposedly belongs to his great-grandfather, Malcolm Foxworth, Robert Moloney. This diary nudges Bart to imagine himself as a conduit for the strength and ambition of his ancestor.
Bart’s newfound influence morphs into danger. He becomes destructive toward his parents and siblings: he lashes out at Jory, even tries to drown Cindy in her baby pool, and the family is shaken when their dog Clover disappears and is later found dead with a twisted piece of barbed wire. While Cathy and Chris notice the changes, only Jory suspects the mysterious neighbor is involved. He also questions the strange overlap between his mother’s life and his father’s history, pondering why Cathy would marry her first husband Paul, who was much older, before Chris.
After Bart nearly dies from tetanus, Jory finally tells Chris about his suspicions regarding Corrine. When confronted, Corrine pleads for forgiveness, but Chris chooses to keep the conflict away from Cathy, deciding not to reveal the truth to protect her. Meanwhile, Cathy suffers a devastating accident and is told she will never dance again. Confined to a wheelchair, she begins to write the story of her life, a manuscript that Bart steals, enraged to learn the shocking truth: Cathy and Chris are brother and sister, and Corrine had locked them in an attic for years to gain an inheritance. This revelation shocks Bart, who clings to the memory of his mother and grandmother even as he becomes emboldened by the notion of power.
Jory’s discovery comes from another source: his paternal grandmother, Madame Marisha Rosencoff—identified as Marisha, the mother of Jory’s biological father Julian Marquet—visits Cathy and challenges her about the family’s tangled past. At first, Jory is stunned and repulsed, but he eventually forgives his parents after confronting the legacy of tragedy that binds them. Cathy finally recognizes Corrine’s voice, and Corrine expresses deep remorse, begging for forgiveness. A confrontation erupts, and John Amos knocks both women unconscious. Acting on John’s orders, Bart, who now believes he is a vessel for his great-grandfather’s vengeful spirit, locks Cathy and Corrine in the cellar with the intention of starving them.
The house catches fire before they can be reached. Bart manages to unlock the cellar, but Corrine urges him to leave them and save himself. She perishes in the blaze, and John dies trapped inside. The epilogue, narrated by Cathy, excerpts her emotional forgiveness of Corrine at Corrine’s funeral and the memory of a family forced to coexist with dangerous secrets in order to protect itself. For the sake of their three children, Cathy and Chris resolve to keep their biological misfortune a secret from the outside world. Bart, tempered by the ordeal, appears to recover from the worst of his madness, yet he remains haunted by the power promised by his great-grandfather’s fortune and the possibility of inheriting it.
