- Bruce Edwards
- Steve Colt
- Virginia Lee
- Joyce Winters
- Carol Forman
- Sombra, The Black Widow
- Anthony Warde
- Nick Ward
- Ramsay Ames
- Ruth Dayton
- I. Stanford Jolley
- Dr. Z.V. Jaffa
- Theodore Gottlieb
- Hitomu
- Virginia Carroll
- Dr. Ann Curry [Chs. 6-7]
- Gene Roth
- John M. Walker - Newspaper Editor
- Sam Flint
- Prof. Henry Weston
- Tom Steele
- Bard [Ch. 1] / Jack [Ch. 8] / Blair [Ch. 12]
- Dale Van Sickel
- Bill [Ch. 4] / Hodges [Ch. 7] / Smith [Ch. 10] / Bass [Ch. 12-13]
- LeRoy Mason
- Dr. Godfrey [Ch. 5]
- Forrest Taylor
- Bradley (Gang Lawyer) [Ch. 10]
- Ernie Adams
- Blinky
- Keith Richards
- Michael Burns [Ch. 1]
- John Alban
- Triangulator Station Tech
- Dave Anderson
- Porter-Spy
- Gordon Armitage
- Detective
- William Bailey
- Morgue Attendant
- Robert Barron
- Link
- George Chesebro
- J. Carter
- Arvon Dale
- Triangulator Station Tech
- Dick Gordon
- Reporter #2 at Demonstration
- Duke Green
- Ted Mills
- Jerry Jerome
- Reporter #1 at Demonstration
- Frank Lackteen
- A. Kabob
- Harold Landon
- Andy Baldwin
- Robert Lawson
- Pilot
- Carey Loftin
- Spike
- Ted Mapes
- Slade
- Frank O'Connor
- Police Inspector
- Jack O'Shea
- Finnegan
- Gil Perkins
- Burke
- John Phillips
- District Attorney Mark
- Stanley Price
- Filmore Hagen
- Bob Reeves
- Detective
- Larry Steers
- Dr. Harcourt
- Laura Stevens
- Trixie
- Charles Sullivan
- Cop with Ruth
- Ken Terrell
- Mendoza
- Frank White
- Lee
- Robert J. Wilke
- Cabbie / Jailer (uncredited)
- Bud Wolfe
- Guard #1 on Cargo Plane
- Peggy Wynne
- Nurse McIntyre
