A woman at home in Liverpool is disturbed by a persistent tapping at her back door. She's disturbed to discover the culprit is a raven, and tries to shoo it away. Which is when the killer strikes.
DS Nathan Cody, still bearing the scars of an undercover mission that went horrifyingly wrong, is put on the case. But the police have no leads, except the body of the bird - and the victim's missing eyes.
As flashbacks from his past begin to intrude, Cody realises he is battling not just a murderer, but his own inner demons too.
And then the killer strikes again, and Cody realises the threat isn't to the people of Liverpool after all - it's to the police.