Every crime scene has a smell. A look. A trail of DNA. It also has a feel. A lingering residue that floats unseen, like bacteria in the air, just waiting to be absorbed. To be felt. To be interpreted. And the man and the boy are the only ones who know this. Veteran major crimes detective Kate Messenger has a problem on her hands: six bodies - father, mother, three children, and the family dog - all slaughtered in their own home, with not a single clue or a shred of DNA that points to the butcher who killed them.