The war lords of a potential enemy of the US has the spy ring, led by John Baroda, the Spy King and his aide Nitra, sabotaging the plans for a vast defense system of radar stations along the American borders. Radar Defense Bureau operative Chris Calvert comes to the rescue of a brilliant radar scientist, Joan Hughes, who has been kidnapped by Baroda henchmen in chapter 1 ("The Fatal Fog"), and the two battle together before putting an end to the Spy King in the aptly-named chapter 12, "Day of Reckoning".
Kirk Alyn
as Chris Calvert
Jean Dean
as Joan Hughes
Anthony Warde
as Ricco Morgan
George J. Lewis
as Lt. Manuel Agura
Eve Whitney
as Nitra
John Merton
as John Baroda
John Crawford
as Sands
Tris Coffin
as Franklyn Lord
