The fingerprints of Ishizawa, a former associate of Yonekura, Onda, and Suemura, are discovered on the bomb planted at the scene of Suemura's murder. Inspectors Otaki and Ayanokoji believe him to be the suspect and head to his home, where they discover him with his hands bound, bleeding from the back of his head. Meanwhile, Keiji goes to Kyoto to investigate Onda, and Conan meets with Haibara, who has been examining the connection between Yonekura, Onda, and Suemura. 15 years earlier, all three were in debt, and all three paid off their debts 10 years ago...