In 1922, Major Herbert Armstrong, a Hay-on-Wye solicitor, was found guilty of, and executed for, poisoning his wife, Katharine, with arsenic. Armstrong's case has all the ingredients of a classic murder mystery, from a plot by Agatha Christie or Dorothy Sayers. It is a near-perfect whodunnit. 100 years later, Stephen Bates examines and retells the story of the case, evoking the period and atmosphere of the early 1920s, a time of newspaper sensationalism, hypocrisy and sanctimonious morality.