A woman has reported to police that she's living in fear because she believes a man who she once regarded as a friend has begun to stalk her. The police are only too aware that they've got to act in case the situation escalates out of control, so they arrest him. One in five women say they've been a victim of stalking, and tougher sentences have recently been introduced to tackle the crime. But the man denies that he's a stalker. Cameras follow the victim and the prime suspect as they argue over whether he has crossed a line and their friendship has now turned into an unhealthy obsession. Police unpick the case as they try to work out who's telling the truth and whether they have the evidence they need to charge the suspect.