- Clayton Moore
- Agent Ted O'Hara
- Roy Barcroft
- Vic Murkland / Commissioner Angus Cameron
- Ramsay Ames
- Frances Blake
- Gil Frye
- Duke Graham
- Tom Steele
- John Parker (Lanky Thug) [Chs. 2, 6] / Gifford [Ch. 7] / Jack [Ch. 11]
- Dale Van Sickel
- Fred Brent (Thug) [Ch. 1-2] / Slocum (Thug) [Ch. 7] / Bud [Ch. 8] / Gill [Ch. 9] / Wilkins [Ch. 12]
- Edmund Cobb
- R.J. Cook
- Stanley Price
- Robert 'Doc' Benson
- Jack O'Shea
- Slater - Benson's Aide
- Barry Brooks
- George (Orderly) [Ch. 8]
- Douglas Aylesworth
- Det. Hayden
- Frank O'Connor
- Dist. Atty. MacLain [Ch. 12]
- Dian Fauntelle
- Miss Stewart [Ch. 3]
- Eddie Acuff
- 'Fiddler' - Used Car Salesman [Chs.3-4]
- Ken Terrell
- Kelsey (Thug) [Ch. 1] / Joe (Camera Thug) [Ch. 6] / Henchman Joe
- Robert Barron
- Garson - Tunnel Detonator Thug [Ch. 1]
- John Crawford
- Duke - Dictaphone Boobytrap Thug [Ch. 5]
- John Daheim
- Henchman Kramer [Ch. 8]
- Arvon Dale
- Moore - Fur-Truck Driver [Ch. 7]
- George Douglas
- Prison Ward Room Guard [Ch. 1]
- Duke Green
- Nichols - Museum Thug [Ch. 10]
- James Linn
- Bailey - Payroll Messener [Ch. 8]
- Carey Loftin
- Hodge - Cook's Killer [Ch. 5]
- George Magrill
- Staley - Trent's Pal in Apartment Looting [Ch. 3]
- Tom McDonough
- Al - Arresting Officer [Ch. 12]
- Tom Monroe
- 2nd Joe - Bomber Pilot Thug [Ch. 8]
- Gil Perkins
- Finch - Welder Thug [Ch. 7]
- Charles Regan
- Hinkey - Finch's Pal [Ch. 7]
- Matty Roubert
- Shipyard Foreman [Ch. 4]
- David Sharpe
- Trent - Apartment Thug [Ch. 3] / Vance - Motorcycle Thug [Ch. 6] (uncredited)
- Charles Sullivan
- Morgan - Roadblock Officer [Ch. 7]
- Glenn Turner
- Dorsey - Laundry Trustee [Ch. 1]
- Phil Warren
- Special Deputy Roberts [Ch.9]
- Russ Whiteman
- Det. Baxter [Ch. 11]
- Robert J. Wilke
- Steele - Phony Detective [Ch. 5]
- Bud Wolfe
- Foy - Motorcycle Thug [Ch. 1]
