Greta, a young American woman, takes a job as a nanny in a remote English village and discovers that the family's 8-year-old is a life-sized doll that the parents care for just like a real boy as a way to cope with the death of their actual son 20 years ago. When she violates a list of strict rules, her worst nightmare is brought to life by a series of disturbing, inexplicable events and she comes to believe that the doll is alive.