Greta, a young woman from Montana, escapes an abusive relationship by getting a temporary job as a nanny for the British Heelshire family. Upon arrival in the United Kingdom and the Heelshire residence, Greta introduces herself to Mr. and Mrs. Heelshire before meeting the elderly couple’s young son, Brahms.
To Greta’s surprise and amusement, Brahms is a porcelain doll, treated like a living child by his “parents”. The real Brahms perished in a fire back in 1991, at the age of eight. Mrs. Heelshire, referring to the porcelain doll, states that Brahms has met “many nannies”, all of whom were “rejected”. Before the Heelshires leave on holiday, they give Greta a list of rules to follow, warning her that Brahms is not a normal child.
Initially, Greta follows a relatively normal routine, choosing to ignore the rules set in place for Brahms. She regularly calls her sister, Sandy, and befriends the Heelshires’ flirtatious grocery boy, Malcolm. Soon after Greta’s refusal to follow Brahms’ rules, strange things begin to happen—a child’s sobs are heard in the hallways, phone calls are cut off and Brahms seems to move on his own, vanishing before reappearing in other sections of the house. Greta finds herself locked in the attic by an unseen force and discovers pictures of the real Brahms playing with a little girl, his childhood friend, Emily. After she is served a peanut-butter-and-jelly sandwich outside her door, she begins to believe that Brahms’ spirit lives on in the doll. Meanwhile, the Heelshires are seen on a coastline writing a good-bye letter to Brahms and filling their pockets with rocks before committing suicide by drowning.
After Greta demonstrates Brahms’ ability to move by himself, Malcolm begins to frequent the house. He informs Greta that the real Brahms was friends with a young girl about his age, who disappeared after a playdate with him in the forest. The girl’s body was later found with her skull crushed. Malcolm warns Greta not to stay in the house, but Greta, having previously suffered a miscarriage, feels obligated to care for Brahms and begins to follow his rules.
One evening, Greta discovers her ex-boyfriend Cole playing snooker in the Heelshires’ home. He questions why she has the doll, and wishes to see the real boy. After establishing that there is not a boy, Malcolm arrives while the three of them eat dinner. Malcolm leaves the house but stays in his car in case anything bad happens. During dinner, Cole shows Greta plane tickets and is determined to bring her home, which she refuses to do, making him angry.