On April 4, 1959, Detective Rokuro Fujisawa takes his dog for a walk. Shortly later, he finds a dead woman. He is able to identify her by searching through her handbag. Her name is Setsuko Ikuta and she worked as a stewardess for an international airline company. She also has a special delivery envelope from the Church Guglielmo. To monitor Detective Rokuro Fujisawa, who is an ace detective, but sometimes uncontrollable, higher ups assigns Yoshitaka Ichimura as Rokuro Fujisawa's new partner. Through intense investigation, Detective Rokuro Fujisawa learns that a blue Renault car with a license plate reserved for foreign residents was parked near the place where the dead woman was found. Detective Rokuro Fujisawa also discovers that the Church Guglielmo possesses a blue Renault.