The Monster in the Box by Ruth Rendell

When Reginald Wexford was starting out as a policeman, he suspected Eric Targo of murder, but had no proof. Over more than thirty years, Targo has stayed in Wexford's mind, and he has kept loose notice of Targo's whereabouts. But after seeing him for the first time in many years, Wexford feels the need to tell his partner and friend, Mike Burden, of his longtime suspicions, including another old murder of which he suspects Targo of being the culprit. Burden isn't convinced, but Wexford presses on. Meanwhile, Burden's wife, Jenny, and DS Hannah Goldsmith take up the cause of a young Muslim woman named Tamima Rahman who they believe might be forced into an arranged marriage. Wexford and Burden feel that the women are poking their noses in where they don't belong. Are Jenny and Hannah overeacting? The Monster in the Box flashes back over the years of Wexford's career in which he met his wife and has children. Fans of this long-running series will be happy for this background material.