Invisible Weapons

First published in the US in 1938, this novel functions as a unique puzzle divided into two distinct halves, presenting two seemingly impossible "invisible" murders that baffle Scotland Yard.

An elderly man named Mr. Robert Fransham is found dead from a brutal blow to the head inside a locked household cloakroom. The case is an absolute paradox: a police officer was inside the house at the time, a chauffeur watched the only outside window, and no weapon capable of inflicting the wound is found inside the room.

Sir Godfrey Branstock dies in his wine cellar from carbon dioxide poisoning. The coroner initially rules it an accidental leak of sewer gas. Scotland Yard's Superintendent Hanslet and Inspector Jimmy Waghorn completely fail to find the answers and drop the investigation. It is only when the analytical Dr. Lancelot Priestley steps in that the brilliant, orderly connections are made to expose how the two deaths are linked by highly inventive, untraceable methods.

Written during the Golden Age of Detective Fiction, the story relies entirely on fair-play puzzle-solving rather than high-stakes action or suspense.
The book showcases the author's background as a military engineer, utilizing creative, scientifically grounded methods to pull off the crimes.