Tapping at my door

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. That's 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.