After Captain Oikawa assigns Sergeant Honma to discover a supposed spy within the Shanghai Military Police, Oikawa's home is bombed, as was a Japanese business a few days ago. At the crime scene, Honma meets Shiozuka, whom he had once investigated for his affiliation with an anti-Japanese magazine. Shiozuka tells Honma he saw there the magazine's ringleader, Kusanagi, who may be involved on it because of his anti-Japanese feeling...