The series stars Takehisa Yamaguchi (Joji Yuki/Riderman in Kamen Rider V3) as secret agent Yutaka Daimon.
Secret Police (秘密刑事, Himitsu Keiji) agent Yutaka Daimon (大門 豊, Daimon Yutaka) returns to Japan after learning his father was murdered by the evil Dr. Akunomiya (悪之宮博士, Akunomiya-hakase), leader of the criminal gang Sigma (Σ団, Shiguma-dan).
Dr. Akunomiya's top aide in Sigma is a woman known as Miss Borg (ミスボーグ, Misu Bōgu).
After his cyborgs and robots (even Miss Borg) have failed to eliminate Yutaka Daimon, Dr. Akunomiya assigns the task of getting rid of his greatest enemy to a young assassin, the motorcycle riding Gen Akizuki (秋月 玄, Akizuki Gen).
Gen Akizuki's bird shaped motorcycle is called Machine Hawk (マシーン・ホーク, Mashīn Hōku).
In episode 40, Yutaka Daimon finds himself up against an even more dangerous group the Dinosaur Army (恐竜軍団, Kyōryū Gundan).
The Dinosaur Army is led by an ancient monster, Triple Neck Demon (魔神三ツ首, Majin Mitsu Kubi).