Stella is married, she has a child and a fulfilling job. She lives with her young family in a house in the suburbs. Her life is happy and unremarkable, but she is a little lonely – her husband travels a lot for work and so she is often alone in the house with only her daughter for company. One day a stranger appears at her door, a man Stella's never seen before. He says he just wants to talk to her, nothing more. She refuses. The next day he comes again. And then the day after that. He will not leave her in peace. When Stella works out that he lives up the road, and tries to confront him, it makes no difference. This is the beginning of a nightmare that slowly and remorselessly escalates.