In February 1915, the Great War is still raging on the Western Front, but in Westminster, at the centre of Hardcastle's bailiwick, a policeman is shot dead. At first, Hardcastle believes the murderer to have been a disturbed burglar. But as enquiries continue, attention focuses on an antiquarian bookseller, a struggling artist, a reporter, officers of the Royal Flying Corps, both in England and in France, and the activities of Isabel Plowman, the wife of one of them and the lover of others.
During Graham Ison's thirty year career in Scotland Yard's Special Branch he was involved in several espionage cases and the investigation into the escape of the spy George Blake. He also spent four years at 10 Downing Street as Protection Officer to two Prime Ministers.