Just after 7 AM DI Helen Grace stumbles on a dead woman lying in a country road. She has been brutally shot for no apparent reason. At gunpoint a shopkeeper is forced to close up by two assailants. Before the police can get inside a single gunshot rings out. Over one long day the town of Southampton is terrorized by two young killers who appear to be killing at random.

For DI Helen Grace, it's a race against time. Uncover why they're doing this and who's next or always be a step behind - until the sun sets on this bloody killing spree.