The Hampstead Mystery - Arthur J. REES

A murder whodunit...
Location: Hampstead, England.
Victim: Sir Horace Fewbanks, a distinguished High Court judge. Cause of death: gun shot wound.
Investigator: Private Detective Crewe, a wealthy bachelor who has taken up crime detection as a hobby, because it provides intellectual challenges more satisfying even than playing twelve simultaneous boards against Russian chess champion Turgieff.
His sidekick: Joe is a fourteen year old Cockney boy, whom Crewe saved from a life of crime by hiring him as a messenger-boy and shadower.
Other whodunit elements: clues galore, suspects in abundance, an inquest, a trial, and an elegant resolution. (Summary by Maikki)