 Boris KarloffJames Lee Wong | James Lee Wong |
 Grant WithersPolice Capt. Sam Street | Police Capt. Sam Street |
 Maxine JenningsMyra Ross | Myra Ross |
 Evelyn BrentOlga Petroff / Countess Dubois / Sophie Dome | Olga Petroff / Countess Dubois / Sophie Dome |
 George LloydDevlin | Devlin |
 Lucien PrivalAnton Mohl | Anton Mohl |
 John St. PolisCarl Roemer | Carl Roemer |
 William GouldTheodore Meisle | Theodore Meisle |
 Hooper AtchleyChristian Wilk | Christian Wilk |
 John HamiltonSimon Dayton | Simon Dayton |
 Wilbur MackRussell | Russell |
 Lee Tung FooTchin | Tchin |
 Lynton BrentTommy | Tommy |
| GGrace WoodMrs. Roemer | Mrs. Roemer |
| FFrank BrunoLescardi (uncredited) | Lescardi (uncredited) |
 Ed CassidyAmbulance Doctor (uncredited) | Ambulance Doctor (uncredited) |
 Wheaton ChambersChemistry Lab Director (uncredited) | Chemistry Lab Director (uncredited) |
 Clancy CooperWarehouse Man (uncredited) | Warehouse Man (uncredited) |
| GGeorge DeNormandJohn (uncredited) | John (uncredited) |
 Lester DorrCoroner (uncredited) | Coroner (uncredited) |
 Herbert EvansWilk's Butler (uncredited) | Wilk's Butler (uncredited) |
| DDick ReinhartDock Worker (uncredited) | Dock Worker (uncredited) |
