Open Verdict: A Mystery (1921) This House to Let (1921) The Lady in Waiting: A Royal Romance (1921) The Marked Man (1921) The Power of the Borgias (1921) The Golden Face: A Great Crook Romance (1922) The Stretton Street Affair (1922) Three Knots (1922) The Voice from the Void: The Great Wireless Mystery (1922) The Young Archduchess (1922) The Bronze Face (1923) as Behind the Bronze Door (US) Where the Desert Ends (1923) A Woman's Debt (1924) Fine Feathers (1924) The Crystal Claw (1924) The Blue Bungalow: A Mystery (1925) The Broadcast Mystery (1925) The Valrose Mystery (1925) Hidden Hands (1926) as The Dangerous Game (US) The Letter "E" (1926) as The Tattoo Mystery (US) Blackmailed (1926) The Fatal Face (1926) The Mystery of Mademoiselle (1926) The Black Owl (1926) The Scarlet Sign (1926) The Lawless Hand (1927) The Chameleon (1927) as Poison Shadows (US) Double Nought (1927) as The Crime Code (US) The Office Secret (1927) The House of Evil (1927) Twice Tried (1928) The Sting (1928) The Rat Trap (1928) Concerning This Woman (1928) The Secret Formula (1928) The Amazing Count (1929) The Crinkled Crown (1929) The Golden Three (1931) Collections Stolen Souls (1895) stories Secrets of Monte Carlo (1899) Secrets of the Foreign Office: Describing the Doings of Duckworth Drew of the Secret Service (1903) Confessions of a Ladies' Man: Being the Adventures of Cuthbert Croom, of His Majesty's Diplomatic Service (1905) The Count's Chauffeur (1906) The Lady in the Car (1908) The Bomb-Makers: Being Some Curios Records Concerning The Craft And Cunning of Theodore Drost, An Enemy Alien in London (1917) Donovan of Whitehall (1917) The Rainbow Mystery, Chronicles of a Colour-Criminologist Recorded by his Secretary (1917) The Secret Shame of the Kaiser (1919) The Hotel X (1919) Society Intrigues I Have Known; Astounding Facts Concerning Prominent People, Disclosed by Lady Betty G---- (1920) Mysteries of a Great City (1920) In Secret (1920) The Luck of the Secret Service; being the Startling Adventures of Claud Heathwaite, C. B., of His Britannic Majesty's foreign office (1921) The Elusive Four, Which Discloses the Exciting Exploits of Four Thieves (1921) The Gay Triangle (1922) Bleke, The Butler: Being the Exciting Adventures of Robert Bleke during Certain Years of His Service in Various Families (1923) The Crimes Club (1927) The Peril of Helen Marklove (1928) The Factotum and Other Stories (1931) Non fiction A Secret Service: Being Strange Tales of