- Dick Purcell
- Captain America / Grant Gardner
- Lorna Gray
- Gail Richards
- Lionel Atwill
- Cyrus Maldor
- Charles Trowbridge
- Dryden
- Russell Hicks
- Randolph
- George J. Lewis
- Bart Matson
- John Davidson
- Gruber
- Norman Nesbitt
- Newscaster
- Frank Reicher
- Lyman [Ch. 1]
- Hugh Sothern
- Eldon Dodge [Chs. 2-5]
- Tom Chatterton
- J.C. Henley [Chs. 6-8]
- Robert Frazer
- Clinton Lyman [Chs. 10-12]
- John Hamilton
- G.F. Hillman [Chs. 13-14]
- Crane Whitley
- Dirk [Chs. 11-12]
- Edward Keane
- Agent 33 [Ch. 15]
- John Bagni
- Monk
- Jay Novello
- Simms [Ch. 1]
- Sam Ash
- Florist #2 [Ch. 1]
- Brooks Benedict
- Florist #1 [Ch. 1]
- Wilson Benge
- Lyman's Butler [Ch. 10]
- Lynton Brent
- Airplane Mechanic [Chs. 8-9]
- Roy Brent
- Nick
- George Byron
- Walt Davis
- James Carlisle
- J.V. Wilson [Ch. 1]
- Ed Cassidy
- Tec-Ni-Gas Co. Gate Guard [Ch. 7]
- James Conaty
- Victim [Ch. 1]
- Lorn Courdaye
- Gas Station Attendant [Ch. 5]
- Hal Craig
- Patrolman #2
- John Daheim
- Dodge Building Thug #2 [Chs. 1-2] / Lab Thug [Chs. 11-12] (uncredited)
- George DeNormand
- Pete
- Kenne Duncan
- Ed Graham [Ch. 14]
- Ben Erway
- Used Car Lot Manager [Ch. 7]
- Al Ferguson
- Detective [Ch. 8]
- J.C. Fowler
- Demonstration Guest
- Terry Frost
- Police Broadcaster [Ch. 3]
- Bud Geary
- Thug at Grant's Office [Ch. 13]
- Fred Graham
- Agent B-10 [Chs. 4, 8-9] / Farm Thug [Chs. 14-15] (uncredited)
- Duke Green
- Platinum Vault Thug [Chs. 3-4] / Nitro-Gas Thug [Ch. 7] (uncredited)
- Ralf Harolde
- Tate - Apartment Thug [Ch. 2]
- Howard Hickman
- Lyman's Attorney [Ch. 4]
- Jerry Jerome
- Eddie the Informer [Ch. 1]
- Jack Kirk
- Express Truck Driver [Ch. 5]
- Glen Knight
- Morgue Wagon Driver [Ch. 11]
- Bert LeBaron
- Airport Thug [Chs. 8-9] / Dynamite Thug [Ch. 10] (uncredited)
- Carl M. Leviness
- Demonstration Guest
- Tom London
- Mack - Garage Thug [Ch. 7]
- Herbert Lytton
- Carl Evans [Ch. 1]
- George Magrill
- Mechanic Thug [Ch. 7]
- Paul Marion
- Morgue Wagon Hijacker #1 [Chs. 9, 11]
- LeRoy Mason
- Bates--Florist #3 [Ch. 1]
- Charles Meakin
- Demonstration Guest
- Frank O'Connor
- Officer at Estate Gate [Ch. 8]
- Jack O'Shea
- Express Truck Crewman [Ch. 5]
- Post Park
- Detective [Ch. 8]
- Gil Perkins
- Barn Thug [Ch. 2] / Hotel Room Thug [Ch. 9] / Waiter Thug [Chs. 13-14] (uncredited)
- Allen Pomeroy
- Cave Thug [Chs. 6-7]
- Stanley Price
- Purple Death Chemist [Ch. 1]
- Jeffrey Sayre
- Norden [Chs. 1-2]
- George Sherwood
- Officer Clancy
- Tom Steele
- Thug at Lyman's [Ch. 1]
- Harry Strang
- Police Mechanic [Ch. 4]
- Robert Strange
- Gang Lawyer [Ch. 12]
- Ben Taggart
- Police Sgt. Donovan [Chs. 5, 9]
- Ken Terrell
- Dodge Bldg. Thug [Chs. 1-2] / Gang Sharpshooter [Ch. 6] / Phony Humane Society Driver [Ch. 10] (uncredited)
- Dale Van Sickel
- Callbox Motorcycle Cop [Ch. 3] / Rick - Phony Humane Society Workman [Ch. 10] (uncredited)
- Edward Van Sloan
- Gregory--Lyman's Aide [Chs. 1-2]
- Robert J. Wilke
- Thug with B-10 [Ch. 4]
- Joe Yrigoyen
- Box Co. Thug [Chs. 5-6] / Barn Thug [Ch. 9] (uncredited)
