Elly is an expert in stalking - an academic at Cambridge University, and a talking head for TV and online, she knows the subject intimately - what motivates a stalker, what drives them, how to rehabilitate them. But when she starts to receive notes saying just 'Me or you' and realises she is being followed, she has become the victim herself. The professional becomes the personal but Elly does not realise quite how personal it is. When she is put in hospital by a stranger pushing her in a crowd, and realises she is in danger, she goes into hiding. But somehow her stalker is still there, watching, waiting.