- Tristram Coffin
- Jeffrey King
- Mae Clarke
- Glenda Thomas
- Don Haggerty
- Tony Dirken
- House Peters Jr.
- Burt Winslow
- James Craven
- Prof. Millard [Chs. 1-7, 10]
- I. Stanford Jolley
- Prof. Bryant
- Douglas Evans
- Chairman [Ch. 12]
- Ted Adams
- Martin Conway [Chs. 1-4]
- Stanley Price
- Gunther Von Strum
- Dale Van Sickel
- Martin - Henchman [Ch.1] / Prof. Drake [Ch. 1] / Gates - Henchman [Chs. 6-7, 9-11]
- Tom Steele
- Knox - Henchman [Chs. 1, 3-4, 7] / Taxi Driver [Chs. 10-11]
- David Sharpe
- Blears - Henchman / Cliff / Stark
- Eddie Parker
- Rowan [Ch. 3]
- Michael Ferro
- Turk - Henchman [Ch. 8]
- Frank O'Connor
- Warehouse Guard [Chs. 1, 10]
- Buddy Roosevelt
- Phillips - Henchman [Chs. 9-10]
- Marshall Bradford
- Prof. Graftner
- Arvon Dale
- Chairman's Aide [Ch. 12]
- Art Gilmore
- Newscaster [Ch. 5]
- Bert LeBaron
- Morgan - Henchman [Chs. 8-9]
- Carey Loftin
- Sparks - Henchman [Ch. 2]
- Jack O'Shea
- Walter - Eastern Electronics' Clerk [Ch. 6]
- Bud Wolfe
- Clay - Motorcycle Rider [Ch. 9]
