In the title story, a young matron from a convalescent home is found dead in a quiet Maida Vale street. The Daily Telegraph ran an article headed 'Murder or Suicide' on the subject of the mysterious death. In 'The Hocussing of Cigarette' an earl's racehorse is the victim of attempted poisoning. 'Who Stole the Black Diamonds' concerns a mystery that bewilders police and diplomats across Europe. All of the twelve detective stories in this volume are puzzled over by Orczy's mysterious armchair detective, the 'Old Man In The Corner'.

Baroness Orczy was born in Hungary in 1865, the daughter of Baron Felix Orczy, a landed aristocrat and well-known composer and conductor. Orczy moved with her parents from Budapest to Brussels and Paris, where she was educated. She studied art in London and exhibited work in the Royal Academy.She married Montagu Barstow and together they worked as illustrators and jointly published an edition of Hungarian folk tales.Orczy became famous in 1905 with the publication of The Scarlet Pimpernel (originally a play co-written with her husband). Its background was the French Revolution and its swashbuckling hero, Sir Percy Blakeney, was to prove immensely popular. Sequel books followed and film and TV versions were later made.Orczy also wrote detective stories which still prove popular and are equally acclaimed within this genre.She died in 1947.