Dr. Masada, a scientist, theorizes that hydrogen bomb testing in the Pacific has created radioactive, liquid mutants— H-Men —that can dissolve and absorb humans on contact.

The story begins with a drug deal gone wrong on the rainy streets of Tokyo. A gangster named Misaki vanishes suddenly, leaving behind only his empty clothes and a bag of narcotics.

Detective Tominaga investigates the disappearance, focusing on Misaki's girlfriend, nightclub singer Chikako Arai.