Darkness & Light by John Harvey is the third book of the Frank Elder mystery series set in contemporary and 1966 England. After Frank retired from the police force, he moved to Cornwall, where he lives simply; a solitary and peaceful life. He misses his daughter Katherine, who's busy with college these days; a tremendous blessing after surviving her abduction and torture (book 2). Frank's ex-wife Joanne asks him to come to Nottingham to investigate a missing person: her friend Jennie's sister Claire. Claire has lived alone, simply and quietly, since her husband died. The police are not concerned about an adult not being home, where her sister came for their weekly Sunday visit. Joanne begs for Frank's help on Jennie's behalf, and Frank agrees, for the most part to be close by Katherine and able to visit her.
In chapters set in 1966, therapist Alice has a disturbed eleven-year-old as a patient. He gets violent at school, and refuses to talk in their sessions, until one day he draws a disturbing sexual picture. Alice suspects he's a victim of sexual abuse. When she raises concerns, his mother withdraws him from school and moves away.
Frank well remembers his first murder case in 1997, because he didn't solve it. When he and his former colleague Maureen Prior (now the detective in charge) view Claire's body, both immediately agree there are too many similarities between the victims to be coincidence. They divide up the investigation: Frank reopens the cold case and re-interviews everyone involved with Irene's last days, while Maureen investigates Claire's recent activities and contacts. Frank and Maureen frequently compare evidence to identify the killer. Before they know for certain who killed Claire, more deaths occur, and the pressure is on the police. Both are compassionate, sensitive to nuance, not prone to jump to an obvious conclusion. Frank realizes not all deaths were committed by the same person.
Very close to the end, we learn the identity of the abused boy and his twisted motivation for murder.