Strike realises that Margot’s killer is responsible for many other murders that have gone undetected, and lays a trap.

Spurred on by the father of a young woman who also went missing in the 1970s, the detectives attempt to outwit an incarcerated serial killer who may hold the key to the case.

The investigation takes a dangerous turn as a disturbing piece of evidence leads Robin and Strike into London’s underworld. Robin risks her life by pursuing a vicious suspect.

Strike is approached by a woman asking for help to find her mother, Margot Bamborough, who went missing in 1974 when a psychopathic serial killer stalked the streets.