Guilty Bonds (1891)

Strange Tales of a Nihilist (1892) [SS]
APA: A Secret Service: Being Strange Tales of a Nihilist (expanded & revised ed. 1896) [SS]

Stolen Souls (1895) [SS]

The Temptress (1895)

Zoraida: A Romance of the Harem and the Great Sahara (1895)

The Great White Queen: A Tale of Treasure and Treason (1896)

Devil’s Dice (1897)

Whoso Findeth a Wife (1897)

A Madonna of the Music Halls (1897)
APA: A Secret Sin; or, The Madonna of the Music Halls (1913)

The Eye of Istar: A Romance of the Land of No Return (1897)

If Sinners Entice Thee (1898)

Scribes and Pharisees: A Story of Literary London (1898)

England’s Peril (1899)

The Veiled Man (1899) [SS]

The Bond of Black (1899)

Wiles of the Wicked (1899)

The Day of Temptation (1899)

Secrets of Monte Carlo (1899) [SS]

An Eye for an Eye (1900)

In White Raiment (1900)

Of Royal Blood: A Story of the Secret Service (1900)

The Gamblers (1901)

The Sign of the Seven Sins (1901)

Her Majesty’s Minister (1901)
APA: The Shadow of a Throne (1901)

The Court of Honour (1901)

The Under-Secretary (1902)

The Unnamed: A Romance of Modern Italy (1902)

The Tickencote Treasure: Being the Story of a Silent Man, a Sealed Script, and a Singular Secret (1903)

The Seven Secrets (1903)

The Three Glass Eyes: A Story of To-Day (1903)

Secrets of the Foreign Office (1903) [SS]
APA: Secrets of the Foreign Office: Describing the Doings of Duckworth Drew, of the Secret Service (1920) [SS]

The Idol of the Town (1904)

As We Forgive Them: Being the Story of a Man’s Secret (1904)

The Closed Book, Concerning the Secret of the Borgias (1904)

The Hunchback of Westminster (1904)

The Man from Downing Street (1904)

The Red Hat (1904)

The Sign of the Stranger (1904)

Behind the Throne (1905)

Sins of the City: A Story of Craft, Crime and Capital (1905)

Confessions of a Ladies’ Man: Being the Adventures of Cuthbert Croom, of His Majesty’s Diplomatic Service (1905) [SS]

The Czar’s Spy: The Mystery of a Silent Love (1905)

The Mask (1905)

The Spider’s Eye (1905)

The Valley of the Shadow (1905)

Who Giveth This Woman? (1905)

The House of the Wicked (1906)

The Mysterious Mr. Miller (1906)

The Mystery of a Motor-Car: Being the Secret of a Woman’s Life (1906)

The Woman at Kensington (1906)

Whatsoever a Man Soweth (1906)

The Secret of the Square (1907)

The Great Court Scandal (1907)

The Great Plot (1907)

Whosoever Loveth: Being the Secret of a Lady’s Maid (1907)

The Count’s Chauffeur (1907) [SS]

Stolen Sweets (1908)

The Crooked Way (1908)

The Lady in the Carr, in Which the Amours of a Mysterious Motorist Are Related (1908) [SS]

The Looker-On: A Romance of Journalistic London (1908)

The Pauper of Park Lane: A Mystery of East and West (1908)

The Woman in the Way (1908)

Fatal Thirteen (1909) [SS]

The House of Whispers (1909)

The Red Room (1909)

Spies of the Kaiser: Plotting the Downfall of England (1909) [SS]

Lying Lips (1910)

The Unknown To-Morrow (1910)

Treasure of Israel (1910)
APA: The Great God Gold (1910)

Hushed Up! A Mystery of London (1911)

Revelations of the Secret Service (1911) [SS]

The Money-Spider: A Mystery of the Arctic (1911)

The Indiscretions of a Lady’s Maid (1911) [SS]

Fatal Fingers (1912)

The Death-Doctor (1912) [SS]

The Mystery of Nine (1912)

Without Trace (1912)

The Lost Million (1913)

The Price of Power, Being Chapters from the Secret History of the Imperial Court of Russia (1913)

The Room of Secrets (1913)

Mysteries (1913) [SS]

Sons of Satan (1914)

The Four Faces: A Mystery (1914)

The German Spy (1914) [SS]

The Hand of Allah (1914)
APA: The Riddle of the Ring (1927)

The Maker of Secrets (1914)

Her Royal Highness (1914)

The White Lie (1914)

At the Sign of the Sword: A Story of Love and War in Belgium (1915)

The Double Shadow (1915)

The German Spy System from Within (1915)

The Mysterious Three (1915)

The Mystery of the Green Ray (1915)
APA: The Green Ray (1934)

The Sign of Silence (1915)

The White Glove (1915)

Annette of the Argonne: A Story of the French Front (1916)

“Cinders” of Harley Street: Being Some Curious Leaves from the Diary of Villiers Beethom-Saunders… (1916) [SS]

Number 70, Berlin: A Story of Britain’s Peril (1916)

The Broken Thread (1916)

The Man About Town (1916)

The Place of the Dragons (1916)

The Spy Hunter (1916) [SS]

The Zeppelin Destroyer: Being Some Chapters of Secret History (1916)

Behind the German Lines (1917) [SS]

No Greater Love (1917)

Rasputin the Rascal Monk; Disclosing the Secret Scandal of the Betrayal of Russia by the Mock-Monk Grichka, and the Consequent Ruin of the Romanoffs (1917)

Beryl of the Biplane (1917) [SS]

The Breath of Suspicion (1917)

The Devil’s Carnival (1917)

Two in a Tangle (1917)

Donovan of Whitehall (1917) [SS]

The Secrets of Potsdam: A Starling Exposure of the Inner Life of the Courts of the Kaiser and Crown-Prince Revealed for the First Time… (1917) [SS]

More Secrets of Potsdam (1917) [SS]

Further Secrets of Potsdam (1917) [SS]

Hushed Up at German Headquarters: Amazing Confessions of Col.-Lieut. Otto von Heynitz… (1917) [SS]

The Bomb-Makers (1917) [SS]

The Rainbow Mystery: Chronicles of a Colour-Criminologist (1917) [SS]

The Scandal-Monger (1917) [SS]

Bolo the Super-Spy: An Amazing Exposure of the Traitor’s Secret Adventures as a Spy in Britain… (1918) [SS]

The Catspaw (1918)

The Little Blue Goddess (1918)

The Minister of Evil: The Secret History of Rasputin’s Betrayal of Russia (1918)

The Secret Life of the Ex-Tsaritza: Amazing Disclosures by Her Maid-of-Honor and Confidante: The Baroness Zeneide Tzankoff (1918)

The Sister Disciple (1918)

The Stolen Statesman (1918)

The Yellow Ribbon (1918)

Sant of the Secret Service: Some Revelations of Spies and Spying (1918) [SS]

Cipher Six (1919)

Rasputinism in London (1919)

Secrets of the White Tsar; The Truth Revealed by His Majesty’s Personal Attache, Colonel Vassili Grigorieff (1919)

The Doctor of Pimlico: Being the Disclosure of a Great Crime (1919)

The Forbidden Word (1919)

The King’s Incognito (1919)

The Lure of Love (1919)

The Hotel X (1919) [SS]

The Secret Shame of the Kaiser (1919) [SS]

No. 7, Saville Square (1920)

The Heart of a Princess: A Romance of To-Day (1920)

The Intriguers (1920)

Mysteries of a Great City (1920) [SS] [reprinted in 1934 in two volumes]
APA: More Mysteries of a Great City (1934) [SS]

The Red Widow; or, The Death-Dealers of London (1920)

Society Intrigues I Have Known: Astounding Facts Concerning Prominent People, Disclosed by Lady Betty G— (1920) [SS]

The Terror of the Air (1920)

Whither Thou Goest (1920)

Mademoiselle of Monte Carlo: A Mystery of To-Day (1921)

The Fifth Finger: A Mystery (1921)

This House To Let (1921)

The Lady-in-Waiting: A Royal Romance (1921)

The Open Verdict (1921)

The Power of the Borgias: The Story of a Great Film (1921)

The Secret Telephone (1921) [SS]

In Secret (1921) [SS]

The Elusive Four: The Exciting Exploits of Four Thieves (1921) [SS]

The Luck of the Secret Service; Being the Startling Adventures of Claud Heathwaite, C. B., of His Britannic Majesty’s Foreign Office… (1921) [SS]

The Golden Face: A Great “Crook” Romance (1922)

The Stretton Street Affair (1922)

The Voice from the Void: The Great Wireless Mystery (1922)

The Gay Triangle: The Romance of the First Air Adventurers (1922) [SS]

Tracked by Wireless (1922) [SS]

The Young Archduchess (1922)

Three Knots (1922)

The Bronze Face (1923)
APA: Behind the Bronze Door (1923)

Where the Desert Ends (1923)

A Woman’s Debt (1924)

Fine Feathers (1924)

The Crystal Claw (1924)

Bleke, the Butlerr, Being the Exciting Adventures of Robert Bleke During Certain Years of His Service in Various Families (1924) [SS]

The Blue Bungalow: A Mystery (1925)

The Broadcast Mystery (1925)

The Marked Man (1925)

The Valrose Mystery (1925)

The Black Owl (1926)

The Fatal Face (1926)

Hidden Hands (1926)
APA: The Dangerous Game (1926)

The Letter E (1926)
APA: The Tattoo Mystery (1927)

The Mystery of Mademoiselle (1926)

The Scarlet Sign (1926)

Blackmailed (1927)

Double Nought; in Which Lionel Hipwell of His Majesty's Foreign Office Recounts His Exciting Adventures following His Follies, and Discloses the Truth concerning the Most Amazing and Desperate Conspiracy, with World-Wide Ramifications (1927)
APA: The Crime Code (1928)

The Chameleon (1927)
APA: Poison Shadows (1927)

The House of Evil (1927)

The Lawless Hand (1927)

The Office Secret (1927)

The Crimes Club: A Record of Secret Investigations into Some Amazing Crimes, Mostly Withheld from the Public (1927) [SS]

Concerning This Woman (1928)

The Rat Trap (1928)

The Secret Formula (1928)

The Sting (1928)

Twice Tried (1928)

The Peril of Helen Marklove and Other Stories (1928) [SS]

The Amazing Count (1929)

The Crinkled Crown (1929)

The Golden Three (1930)

Scandals of Society (1930) [SS]

The Factotum and Other Stories (1931) [SS]