Lloyd Hughes

as Eddie Carter

as Dr. Craig Mitchell

as John Ainsworth

as Dr. Steven Russell

as Daubeney Carshott

as Capt. Jerry Brown / Jim Lofton

as Doctor Marshall

as Dr. Marshall, 'The Scorpion'

as Curtis Powell

as Agent Ted Kelly

as Owen Rogers

as Frank Gordon

as Bruce Donaldson

as Lieut. Dan Burke

as Ted 'Rip-Roaring' Riley

as Andrew Robinson

as Capt. John Kent

as Fred Truslow

as Graham Smith

as Henry Townsend

as Attorney Johnson

as Jimmy Milligan

as Robert Thornton

as Daniel Treve

as Bill Ramsey

as Tony Hill

as Bart Wallace

as Bob Rogers

as Dr. Robert Sanford

as Prince Nicholas Petroff

as Fred Garlan

as Derek

as Bill

as George Edward Blaine

as Jack

as Marshall Jones

as Johnny Stark

as Dr. Bradford

as Nikolai Roget

as Bobby Bailey

as Philip Lennox

as Cal

as Don Manning

as Hayden Eaton

as Jerry Booth

as Franz Pless

as John Barton

as Jerry

as Felipe

as Gil Barry

as Theodore Wayne

as Richard Castleman / Danny Rowland

as Waite Lifter

as Julian Perryam

as Donald Marshall

as Philip Collett

as Phil Douglas

as Rance Conway

as Ned Thayer

as Blair Farquar

as Charlie Jordan

as Edward E. Malone

as The Hero

as Julian Greer

as Ned Tyler

as Lionel Tressilian

as Robert Ardis

as Dick Forrest

as Jack Hare

as John Trevor

as Sam Gladding

as Harvey Livermore

as Oliver Wendell Blaine

as Cody Jacques

as Frederick Graves

as David Beresford

as John Trott

as Robert Sheldon

as Dick Revel

as Himself

as Luther Flint

as Roger Moran

as John King

as Roland

as Dick Armitage

as Dick Ross

as Paul Perry

as Tad Worden

as Jules Patricia

as Ted Marshall

as Reporter (uncredited)