Unsure about her future, recent college graduate Annie (SCARLETT JOHANSSON) takes a job as a nanny for an Upper East Side couple. Seeing the job as temporary and a kind of anthropological adventure, Annie deems them Mr. and Mrs. X (PAUL GIAMATTI and LAURA LINNEY), narrating as if she's Mary Poppins writing a field diary -- complete with umbrella and objective insight with which to save the child, Grayer (NICHOLAS ART), from the parents she perceives as distracted and self-absorbed.
Once hired, Annie begins describing her own frustrations: Mrs. X calls her "Nanny" (not by her name), expects her to handle diurnal details (picking up Grayer from school, taking him to the park) as well more sophisticated tasks (teaching him French), and refuses to acknowledge her employee might have any life outside her live-in job.
When Annie is attracted to the Xes' upstairs neighbor, whom she calls the Harvard Hottie (CHRIS EVANS), she worries she'll be fired for even thinking about a date, and so she begins lying to her boss. This on top of lies she's telling her New Jersey-based mother (DONNA MURPHY), who believes Annie is living in the city with her best friend Lynette (ALICIA KEYS), making lots of money at a high finance firm.
Annie worries for a while about Grayer, earnestly thinking she must stay in place to protect him. But soon enough, following the formulaic plot, she learns some lessons about telling the truth (to herself as well as others), repackages those lessons for Mrs. X, and frees herself from deception and self-delusion.