The intruder is none other than legendary LAPD detective Harry Bosch, hunting for leads in an unsolved case that has got under his skin.
Ballard escorts him out but - curious to know what he was searching for - soon becomes obsessed by the murder of Daisy Clayton. Was she the first victim of a serial killer who still stalks the streets?
For Bosch, the case is more than personal: it may be all he has left.
But in a city where crime never sleeps, even detectives have a dark side...