Plot
Greta Evans, an American travelling in the United Kingdom, is hired as a nanny by the elderly Heelshires. The couple introduce Greta to her charge, a doll named Brahms, which the Heelshires treat as if it were their real son. They coach Greta on taking care of Brahms and their house while they are on holiday.
Greta ignores the rules. She regularly calls her sister, who tells her that Greta's abusive ex-boyfriend Cole has been trying to find out where she is. Malcolm, the Heelshires' "grocery boy", stops by often, and Greta learns from him that the real Brahms was killed in a fire 20 years ago on his eighth birthday. Malcolm asks Greta out and she accepts. While showering for her date, her dress and jewellery vanish. She investigates a noise in the attic, but ends up getting trapped and inadvertently knocked unconscious, missing her date. She explains to Malcolm what happened, and they discuss the real Brahms, whom Malcolm says Mr. Heelshire described as "odd".
Strange events occur. Greta locks herself in her room. She then finds a peanut butter and jelly sandwich outside her door and a child's voice promises he will be good. Greta begins to take the rules seriously.
She realizes that the doll only moves when she is not in the room with him. Malcolm informs Greta that a girl Brahms was friends with (named Emily Cribbs) was found in the forest with her skull crushed. Afterwards, the Heelshires' house was burnt down with him in it. Malcolm warns her not to stay but Greta feels obligated to care for Brahms, believing that the child's spirit is possessing the doll. The Heelshires write a goodbye letter to Brahms before drowning themselves.
Cole arrives unexpectedly, demanding Greta return to America with him in the morning. Malcolm arrives and offers his help, but she declines it, so he leaves, but stays in his car to be nearby. Greta asks the doll for help and Cole wakes up and sees a message written in blood telling him to leave. Cole gets angry and Malcolm comes back in to investigate the commotion. Cole smashes the doll to pieces, which causes the house to begin to shake, and they hear noises behind the walls. A mirror explodes and the real, living Brahms — a full grown man, who had been hiding in the walls and wearing a doll mask — emerges from it and kills Cole.
Greta and Malcolm flee into the wall cavity where the real Brahms had been hiding, and discover Brahms' room, along with a female doll dressed in Greta's stolen dress. Brahms knocks out Malcolm but Greta is able to escape the house, before returning to save Malcolm. She realizes Brahms is still child-like, and invokes the rules and forces Brahms to bed. He asks for a good night kiss, which Greta gives and uses it as a distraction to stab him. Brahms tries to choke her but she pushes the weapon in deeper and he collapses. Greta rescues Malcolm and they escape.
In a final scene, someone is seen repairing the doll.
