Howard St. John as David Harding Amanda Blake as Karen Michele Ron Randell as Simon Langton June Vincent as Barbara Taylor Fred Sears as Peters John Dehner as Robert Reynolds Lewis Martin as Dr. Victor Gilbert, also known as Hugo Boren Rick Vallin as McCullough Jimmy Lloyd as Burton Ted Jordan as Brown Gregory Gay as Professor Schuman Douglas Evans as Colonel Kilgore John Doucette as Larry, a thug Don Brodie as Jimmy, a thug Gene Autry as Gene Autry Sheila Ryan as Carol Bannister Robert Livingston as Sam Brady Frank Jaquet as Clayton Hodges Vince Barnett as Barber Mulkey Syd Saylor as Skeeter Sandy Sanders as Bud Pat Buttram as Smokey Argyle Gregg Barton as Keg Rollins Kenne Duncan as Latigo Roy Gordon as John MacKnight Stanley Andrews as Chalmers Robert Hilton as Bancroft Robert J. Wilke as Bradshaw John Miljan as Judd Holbrook Robert Carson as Bill Cummings Pat O'Malley as Charley Stewart John McKee as Wilson Champion as Gene's Horse