51. You Are Rider Number 4!!

Marshal Armor has developed a powerful Pluton Rocket that is more powerful than the H-Bomb and the Great Leader orders that it be aimed at Tokyo. Shiro and Joji become suspicious when a group of mountaineers are killed mysteriously in a remote valley. While investigating, they are attacked by mutant Crawganna who protects the Destron missile base. But, V3 and Riderman fail to stop Marshal Armor from starting the cataclysmic countdown�