Someone poisons Black Rabbit Restaurant employee Yuri's drink with arsenic. The suspects are narrowed down to Morooka,, Fukamachi, and Sana. Conan and Amuro determine the truth based on Yuri's fake nail discovered by Ran and a casual comment from Kogoro. Conan interrupts Megure as he's questioning the suspects, telling him two of them couldn't have been the cuprit based on their words and actions, and gradually closes in on the culprit as he reveals the trick they used. After the case is resolved, Amuro uses a spare key to break into the Kudo family residence. Amuro and Okiya Subaru, both armed with guns, end up face to face..

The body of Kadowaki Eiji is discovered in Beika Park with his head split open. Eiji was the problem child of the Kadowaki family. According to rumor, Eiji abused his mother Yasuko, and his older brother Yuichi would try to stop him. It also becomes clear that a suspicious man was investigating the Kadowaki family. Inspector Megure suspects Yuichi, but Yuichi has an alibi for the time of the crime. Later, they learn the suspicious man was Takase, a student of former grade school teacher Yasuko. The police go to question Takase, but...