"Anna Klein is ready to return to work for the first time since having children. She and her husband, Josh, decide to hire a live-in nanny with some trepidation, but all their misgivings disappear as soon as they meet Oaklynn Durst. She has stellar references, a calm disposition, and a natural way with children. Not to mention their kids simply adore her. But not long after Oaklynn arrives, the children start to come down with the most puzzling illnesses...