Dr. Cygnus Layton
Dr. Bryant
Commodore Carlson
Man in Audience (1 episode)
John Greer (1 episode)
Captain Hornsby
Daniels (uncredited)
Vero (uncredited)
Prof. Millard
Henry Mills
Brigadier General (uncredited)
M. De Treville
Dr. Bryant
Swenson (uncredited)
Stage Actor Playing Philip Mannings
Commishioner Litchfield
Prof. Millard
John Wheeler
Prof. James Clayton [Chs. 1, 10-12]
Dr. George Strong
Mordigan
Cal Sutton
Interpreter (uncredited)
British Major
Cavalier (uncredited)
Bismo - Annabella's Friend (uncredited)
Winsley (uncredited)
Mr. Winters
Ace Diamond
Dr. Cyrus Layton
Major Morris
Commissioner Robert George Hardy [Chs. 5-7]
Officer (uncredited)
Thomas (uncredited)
Lloyd Chapin
Ship's Radio Man (uncredited)
Fire Warden
Ivan Shark
Guard (uncredited)
Joseph Rand
Giovanni (Uncredited)
Instructor
Captain in Car (uncredited)
Dan Slocum
'Dandy' Darnell
Abel Bellamy