Characters

• 

  Dr. Mark Steel

  Played by: Lon Chaney Jr.
• 

  Prof. Norman Reed

  Played by: Lon Chaney Jr.
• 

  David Stuart

  Played by: Lon Chaney Jr.
• 

  Alex Gregor, aka Gregor the Great

  Played by: Lon Chaney Jr.
• 

  Jeff Carter

  Played by: Lon Chaney Jr.
• 

  Wayne Fletcher

  Played by: Lon Chaney Jr.
• 

  Nina Coudreau

  Played by: Elena Verdugo
• 

  Margaret Mercer

  Played by: Lois Collier
• 

  Stella Madden

  Played by: Patricia Morison
• 

  Maria Steele

  Played by: Ramsay Ames
• 

  Mrs. Duval

  Played by: Fay Helm
• 

  Robert 'Bob' Duval

  Played by: David Bruce
• 

  Inspector Gregg

  Played by: J. Carrol Naish
• 

  Dave Curtis

  Played by: Lloyd Bridges
• 

  Prof. Millard Sawtelle

  Played by: Ralph Morgan