In The Secret Hangman, Police Superintendent Peter Diamond has to contend with a female admirer, a theft ring, and a series of hangings. Peter Lovesey's hero manages all three, but does better with the hangings and the admirer than with the theft ring.

Lovesey switches easily between Diamond's professional and private lives. The various police team members aid the investigation, but at times complicate Diamond's life. His boss demands results and sometimes interferes. He teeters on the edge of insubordination.

The murder of his wife three years ago still haunts Diamond. Too busy for a social life, he literally drives into a situation with a strange woman, but discovers a warm and caring person. Tentative at first, he soon commits himself to a new relationship. The woman also has an adult son active in a local church and who volunteers at local hospitals.

The first woman found hanging on children's swing set in a public park is considered a suicide, but an added ligature mark on neck says otherwise. Then the police find her ex-partner and father of her children hanging from a viaduct. They consider him the murderer who then committed suicide. However, Diamond puzzles over the motivation and seeks to learn more about both people.

At times Lovesey tells the reader more than the story requires about historical trivia. He exploits the area around Bath with skill. Caves figure prominently in the story.

Enough red herrings make for an interesting read. A few inconsistencies and unexplained loose ends may annoy the astute reader, but most Diamond fans won't care. They will eagerly await the next case in the Peter Diamond Investigation series.