A seagull agent who infiltrated Japan from Pyongyang plans to smuggle a large amount of drugs into South Korea. The Korean Anti-Aircraft Investigation Office, which has decrypted the radio, disguises an investigator as a foreign sailor and infiltrates Fukuoka. The undercover investigator meets the drug and detective head of the Japanese Metropolitan Police Agency, disguised as a detective named Kurogami. Keiko's father, Katsuo, who has finished serving his sentence as a smuggler, fights over the drug hidden between the Seagull and the investigator. In the place where everyone gathers around drugs, Japanese prisoners led by Chief Kurogami raid and arrest all of them, and the conspiracy on the Pyongyang side is destroyed.