Maeve Kerrigan is used to investigating murders.But this time a killer has struck far too close to home...

When a police officer is found shot dead in his car, DC Maeve Kerrigan and DI Josh Derwent take on the investigation. But nothing about the case prepares them for what happens next: a second policeman dies . . . and then another . . .

The Metropolitan Police struggle to carry out their usual duties, but no one knows where or how this cop killer will strike again. While London disintegrates into lawlessness Maeve's world starts to fall apart too. For if the police can't keep themselves safe, how can they protect anyone else?