The Four Men of the title are British WWI veterans who decide to work secretly against enemies of the country. They aren't above a bit of murder or sabotage to serve their ends, but they consider themselves to be true patriots.
Hugh Sinclair
Humphrey Mansfield
Griffith Jones
James Brodie
Francis L. Sullivan
Leon Poiccard
Frank Lawton
James Terry
Anna Lee
Ann Lodge
Alan Napier
Sir Hamar Ryman M.P.
Basil Sydney
Frank Snell
Lydia Sherwood
Myra Hastings
Edward Chapman
B.J. Burrell
Athole Stewart
Police Commissioner
George Merritt
Inspector Falmouth
Garry Marsh
Bill Grant
The Deadly Affair
Shuffle
Overdrive
Stowaway
The Commuter
The Quiller Memorandum
Run
All the Devils Are Here
Night Watch
The International
Trigger Point
Hunting Season
Asylum
God Is a Bullet
The System
Hellion
Seeking Justice
Supercross
The Engineer
Blood Ties