Lionel Atwill

as Police Inspector Holtz

as Alec Ritchfield

as Inspector Arnz

as Charles Finch

as Cyrus Maldor

as Mayor of Vasaria

as Professor Moriarty

as Dr. King

as Varnoff

as Dr. Fish

as Dr. Bohmer

as Rawitch

as Dr. Ralph Benson, posing as Graham

as Dr. Paul Rigas

as Harry Compton

as Dr. Suderman

as Jim McLaughlin

as Cliveden Compton

as Paul Messenger

as Prof. Roger Chauncey Hildebrand

as Walter Stevens

as Dr. James Mortimer

as De Rochefort

as Inspector Krogh

as Count Anton 'Tony' Hohenfried

as Breuer

as M. Beaumarchais

as Maj. Gen. Sir John Sangye

as Col. Vigo

as Gerald A. Axton

as Colonel Bishop

as Maj. William Brennan

as Captain Cole

as Capt. Don Pasqual 'Pasqualito' Costelar

as Inspector Neumann

as Julius Beaufort

as Herr Von Sturm

as Robert von Helldorf

as Baron von Merzbach

as Jerome Breen

as Eric Gorman

as Ivan Igor

as Dr. Otto von Niemann

as Dr. Jerry Xavier