Boris Karloff
Dr. John Garth
A physician on death row for a mercy killing is allowed to experiment on a serum using a criminals' blood, but secretly tests it on himself. He gets a pardon, but finds out he's become a Jekyll-&-Hyde.
Dr. John Garth
Martha Garth
Dr. Paul Ames
Capt. McGraw
Dr. Ralph Howard
Warden Thompson
Victor Sondini
George Wharton
Stephen Barclay
District Attorney
Otto Kron - Convict
Anson, Prison Guard
Sam - Hospital Prison Orderly
Governor Prentiss
Dr. Nichols
Mandish
Reardon
Sanders
Patrolman Olson
Judge Braden
Director
