 Frank BuckFrank Hardy | Frank Hardy |
 Sasha SiemelTiger Van Dorn | Tiger Van Dorn |
 Reginald DennyRalph Marshall | Ralph Marshall |
 Esther RalstonValerie Shields | Valerie Shields |
 Charlotte HenryDorothy Elliott | Dorothy Elliott |
 William BakewellTom Banning | Tom Banning |
 Clarence MuseLightning | Lightning |
 Willie FungChiang-Houseboy | Chiang-Houseboy |
 LeRoy MasonJim Murphy | Jim Murphy |
 Matthew BetzInspector Starrett | Inspector Starrett |
 Richard TuckerRobert Banning | Robert Banning |
 Duncan RenaldoArmand Roget | Armand Roget |
 Fred Kohler Jr.John Charles | John Charles |
 Sherwood BaileyPaul Marshall | Paul Marshall |
 Harry 'Snub' PollardCampbell | Campbell |
| GGeorge RosenerProfessor | Professor |
 Gertrude SuttonMrs. Maitland | Mrs. Maitland |
 John St. PolisChandler Elliott | Chandler Elliott |
 John DavidsonDoctor Coleman | Doctor Coleman |
 Milburn MoranteSingapore Joe | Singapore Joe |
| DDirk ThaneJoe Nolan | Joe Nolan |
 Robert WarwickAngus MacLeod | Angus MacLeod |
| DDahlam AliHardy's Assistant | Hardy's Assistant |
 Jim CoreyHenchman | Henchman |
 Paul EllisGreenway | Greenway |
| HHenry HaleJackson | Jackson |
 Harry HarveyRoget Clerk #1 | Roget Clerk #1 |
| RReed HowesSailor | Sailor |
 Jack IngramUndercover Detective at Dive | Undercover Detective at Dive |
 Tom LondonDetective Interrogating Pete | Detective Interrogating Pete |
