James Craven

as Roy

as Dr. Cygnus Layton

as Dr. Bryant

as Drake

as Commodore Carlson

as Daniels (uncredited)

as Captain Hornsby

as Vero (uncredited)

as Prof. Millard

as Henry Mills

as Brigadier General (uncredited)

as Dr. Bryant

as Swenson (uncredited)

as M. De Treville

as Stage Actor Playing Philip Mannings

as John Wheeler

as Prof. Millard

as Prof. James Clayton [Chs. 1, 10-12]

as Commishioner Litchfield

as Cal Sutton

as Interpreter (uncredited)

as British Major

as Mordigan

as Dr. George Strong

as Bismo - Annabella's Friend (uncredited)

as Cavalier (uncredited)

as Winsley (uncredited)

as Bidwell

as Mr. Winters

as Ace Diamond

as Dr. Cyrus Layton

as Major Morris

as Commissioner Robert George Hardy [Chs. 5-7]

as Officer (uncredited)

as Fire Warden

as Ship's Radio Man (uncredited)

as Thomas (uncredited)

as Ivan Shark

as Guard (uncredited)

as Lloyd Chapin

as Joseph Rand

as Dan Slocum

as Instructor

as 'Dandy' Darnell

as Giovanni (Uncredited)

as Captain in Car (uncredited)

as Abel Bellamy

as Man in Audience

as John Greer