In the queue for the toilets at Gatwick, a teenage girl catches 57-year-old Margaret Benson's eye in the mirror and mouths the world help. Margaret's reaction leads to the dramatic rescue of the teenager from her trafficker and Margaret becomes a hero.

But when the story gets picked up by the papers, Margaret is panicked by the publicity, as well as the strange phone calls she begins to receive. Meanwhile Anja makes contact. She wants to thank her rescuer, but she also quickly inserts herself into Margaret's lonely life. As their friendship develops, so do questions: who is Margaret hiding from, and what are Anja's true motives? And what is the cost of living a lie?