- Eduardo Ciannelli
- Doctor Satan
- Robert Wilcox
- Bob Wayne / 'Copperhead'
- William Newell
- Speed Martin
- C. Montague Shaw
- Prof. Thomas Scott
- Ella Neal
- Lois Scott
- Dorothy Herbert
- Alice Brent
- Charles Trowbridge
- Gov. Bronson [Ch. 1]
- Jack Mulhall
- Police Chief Rand [Chs. 1, 4, 13]
- Edwin Stanley
- Col. Bevans
- Walter McGrail
- Stoner
- Joe McGuinn
- Gort
- Bud Geary
- Hallett
- Paul Marion
- Corbay [Ch. 1]
- Archie Twitchell
- Ross
- Lynton Brent
- Scarlett [Chs. 1-5]
- Ken Terrell
- Corwin
- Al Taylor
- Joe [Chs. 9-15]
- George Allen
- Henchman-Driver Spike [Ch. 8-9]
- John Bagni
- Gray - Pick-up Thug [Chs. 14-15]
- Frank Brownlee
- Panamint Pete [Ch. 8]
- James Bush
- Co-Pilot [Chs. 12-13]
- Yakima Canutt
- Sailor at Winch [Chs. 3-4]
- Virginia Carroll
- Nurse [Ch. 11]
- Ed Cassidy
- Barton [Ch. 1]
- Davison Clark
- Police Lieutenant [Ch. 7]
- Tris Coffin
- Wells -Governor's Secretary
- Tristram Coffin
- Wells - Governor's Secretary [Ch. 1]
- Frank Conklin
- Burns - Station Master [Chs. 8-9]
- Fred Criswell
- Officer [Ch. 11]
- Eddie Dew
- Gas Station Attendant [Ch. 4]
- Frank Ellis
- Plant Henchman [Chs. 10-11]
- James Fawcett
- Al
- Sam Garrett
- Roper
- Duke Green
- Duke - Mine Thug [Ch. 9]
- Alan Gregg
- Red - Mine Thug [Ch. 9]
- Kenneth Harlan
- Capt. Lathrop [Chs. 1-2]
- Charles Hutchison
- Proprietor [Ch. 5]
- Jerry Jerome
- House Heavy [Ch.15]
- Patrick Kelly
- Plant Henchman [Chs. 10-11]
- Marten Lamont
- Steve - Pilot [Chs. 12-13]
- Bert LeBaron
- Fallon - Henchman [Chs. 10-11]
- Jack O'Shea
- House Heavy [Ch. 15]
- Eddie Parker
- Chuck - Lead Truck Thug [Chs. 8-9]
- Hal Price
- P&G Warehouse Mgr. [Ch. 10]
- Ernest Sarracino
- Henchman-Guard [Ch. 2]
- Cy Schindell
- Jake - Biplane Pilot [Ch. 2]
- William Stahl
- Detective Brock
- Ted Stanhope
- Warehouse Watchman [Ch. 7]
- Tom Steele
- Truck Henchman
- Harry Strang
- Davis - Police Officer [Ch. 1]
- Duke Taylor
- Watkins - Fire Escape Thug [Chs. 6-7]
- Robert Wayne
- Detective Perry
- Wally West
- Palmer - Thug [Chs. 5-6]
- Lloyd Whitlock
- Prof. Williams [Chs. 12-14]
- Bill Wilkus
- Truck Henchman [Chs. 8-9]
- Bud Wolfe
- Sailor at Cable [Chs. 3-4]
