They find a seemingly faultless applicant in twenty-five-year-old Abby. Flawlessly efficient and utterly devoted, she seems absolutely ideal. Except to the Eastman's neighbor, Mel Olsen, who's caught the lovely sitter in mid-seduction with his teenage son. She's also arousing a dirty little suspicion in Carter's aggressive, alcoholic partner, Tate Walker. As they're all about to learn, cross this nanny and she'll bite. Tate is discovered dead in his car at the bottom of the lake, and Mel suffers a deadly mishap at home. It's not until Meghan suffers a suspicious accident that she engages her colleague, Shelly Pierson, to delve into Abby's history. What they discover is the strange story of a young girl's tragic death at the hands of an abusive mother, the troubling fate of an elderly woman confined to a state mental hospital, and an unexpected secret that touches the darkness of Carter's own past. All of these pieces fit into the puzzle of a young woman's insane mission of revenge and retribution. Tonight, this nanny's going to be working overtime.