Claire and Michael Bartel are a married couple living in the peaceful suburbs with their young daughter, Emma, and a baby boy on the way. When Claire seeks the care of an obstetrician, Dr. Mott, she is subjected to inappropriate behavior, leading her to report him. As a result, Dr. Mott is stripped of his license and subsequently commits suicide, leaving his pregnant wife devastated. Distraught and financially ruined, Mrs. Mott loses her unborn baby and vows revenge on Claire. She changes her name to Peyton Flanders and applies for the position of nanny in the Bartel household, winning the family's trust with her charm and seemingly impeccable references.

As Peyton integrates into the family's life, she subtly begins to manipulate and undermine Claire, sowing seeds of doubt and discord while appearing to be the perfect caregiver. Her calculated actions are aimed at destabilizing the family structure from within, creating rifts between Claire and Michael, and threatening the safety of their children. Peyton's true intentions slowly unravel, revealing the extent of her malicious plan. Unaware of the danger lurking in their home, the Bartels' lives spiral into chaos as Peyton's influence grows, setting the stage for a dramatic confrontation.