- Marten Lamont
- Jerry Blake
- Helen Talbot
- Joyce Kingston
- George J. Lewis
- Jim Belmont
- Lorna Gray
- Rita Parker
- Hal Taliaferro
- Matt Farrell
- LeRoy Mason
- Morton [Chs. 1, 9-10]
- William Stevens
- Agent Fred Martin
- Maurice Cass
- Signor Giuseppe Morello [Ch. 11]
- Kernan Cripps
- Agent Thomas Jeffries [Ch. 1]
- Elaine Lange
- Countess Delremy [Ch. 1]
- Frank Jaquet
- Warren Hunter [Ch. 2]
- Forrest Taylor
- Otto Wolfe [Ch. 7]
- Jay Novello
- Heinrick [Ch. 2]
- Tom London
- Prof. Crawford [Chs. 5-6]
- Jack Ingram
- Riggs [Ch. 1]
- Ernie Adams
- Tony
- Curt Barrett
- Photographer
- George Chesebro
- Solko
- Edmund Cobb
- Officer Corwin
- Michael Gaddis
- Benson
- Jack George
- Signor Roberto Carlotti
- Fred Graham
- Hinds
- Duke Green
- Clay / Lacy (uncredited)
- Fred Howard
- Ed Atkins
- Jack Kirk
- Mr. Hood
- Craig Lawrence
- Austin
- Nolan Leary
- Jim
- Rex Lease
- Bower
- Frank Marlowe
- Mack
- Jack O'Shea
- Baker
- Stanley Price
- Monte Mason
- Walter Shumway
- Joe / Policeman (uncredited)
- Tom Steele
- Johnny Daniels / Mr. Snyder / Thug Guard / Agent Posing as Trucker / Dorgan / Gorman (uncredited)
- Harry Strang
- Bank Vault Manager
- Ken Terrell
- Norton Corby
- Dale Van Sickel
- Carlson / Clark / Sands Alley Henchman / Sharon (uncredited)
- Jimmy Zahner
- Messenger
