- Walter Reed
- Kent Fowler
- Lois Collier
- Helen Hall
- Gregory Gaye
- Mota
- James Craven
- Bryant
- Harry Lauter
- Drake
- Richard Irving
- Ryan
- Sandy Sanders
- Steve
- Michael Carr
- Trent
- Dale Van Sickel
- Watchman [Ch. 1]
- Tom Steele
- Taylor
- George Sherwood
- Gate Guard [Ch. 7]
- Jimmy O'Gatty
- Grady
- John De Simone
- Curtis [Ch. 8]
- Lester Dorr
- Crane [Ch. 7, 11]
- Dick Cogan
- Kirk [Ch. 7]
- Barry Brooks
- Policeman in Bryant's Lab [Ch. 8]
- Dick Crockett
- Cave Thug #2 [Ch. 5]
- John Daheim
- Boyd, Shipping Clerk [Chs. 4-5]
- Sol Gorss
- Cave Thug #1 [Ch. 5]
- Paul Gustine
- Technician [Ch. 1]
- Chuck Hamilton
- Truck Driver [Ch. 4]
- Carey Loftin
- Truck Loader-Thug [Chs. 7-8]
- David Sharpe
- Technician [Ch. 1]
- Guy Teague
- Plant Guard [Ch. 6]
- Ken Terrell
- Graves, Mechanic [Ch. 3]
- Bill Wilkus
- Pilot [Chs. 1-2, 10]
