Lloyd Hughes

as Eddie Carter

as Dr. Steven Russell

as Daubeney Carshott

as Dr. Craig Mitchell

as John Ainsworth

as Capt. Jerry Brown / Jim Lofton

as Dr. Marshall, 'The Scorpion'

as Doctor Marshall

as Owen Rogers

as Bruce Donaldson

as Agent Ted Kelly

as Curtis Powell

as Frank Gordon

as Graham Smith

as Henry Townsend

as Capt. John Kent

as Ted 'Rip-Roaring' Riley

as Lieut. Dan Burke

as Attorney Johnson

as Andrew Robinson

as Fred Truslow

as Robert Thornton

as Jimmy Milligan

as Tony Hill

as Bill Ramsey

as Dr. Robert Sanford

as Prince Nicholas Petroff

as Daniel Treve

as Bart Wallace

as Bob Rogers

as Johnny Stark

as George Edward Blaine

as Derek

as Fred Garlan

as Jack

as Marshall Jones

as Bill

as Bobby Bailey

as Nikolai Roget

as Dr. Bradford

as Don Manning

as Philip Lennox

as Cal

as Franz Pless

as Jerry

as Jerry Booth

as John Barton

as Hayden Eaton

as Donald Marshall

as Julian Perryam

as Gil Barry

as Theodore Wayne

as Waite Lifter

as Felipe

as Richard Castleman / Danny Rowland

as Philip Collett

as Edward E. Malone

as Phil Douglas

as Rance Conway

as Blair Farquar

as Ned Thayer

as Charlie Jordan

as John Trevor

as Lionel Tressilian

as Dick Forrest

as Ned Tyler

as Robert Ardis

as Julian Greer

as Jack Hare

as The Hero

as Oliver Wendell Blaine

as Harvey Livermore

as Sam Gladding

as Cody Jacques

as Frederick Graves

as David Beresford

as John Trott

as Dick Revel

as Robert Sheldon

as Luther Flint

as Roger Moran

as Himself

as Tad Worden

as Dick Ross

as Roland

as Paul Perry

as Dick Armitage

as John King

as Reporter (uncredited)

as Jules Patricia

as Ted Marshall