Samantha (Melissa George) is an espionage operative for "Byzantium", a private intelligence agency. She survives an attempt on her life, which she strongly suspects was orchestrated by members of the company she works for. After recovering and returning to active duty, she goes back to work undercover as a nanny, not knowing who tried to kill her or whom to trust. It becomes evident that the attempt on her life is tied into a horrific event from her childhood.