While out on a trip for their homework assignment, Conan and the Junior Detective league rescue a young girl being assaulted. She later comes to the detective agency to speak with Kogorou. They decide to investigate after learning that a treasure is involved. During their travel to Tsuwano, the young girl meets with her friend, who seems suspicious. While investigating, the girl, Haibara, and Mitsuhiko are abducted.

Kogoro is invited to a wine appreciation party by Shiratori. While there, Conan witnesses an argument between two men and sees one attack the other. When he finally arrives at the crime scene, there is no sign of the attacked man. The other man is obviously hiding him, but Conan cannot seem to find proof. After finding a reason to trick people into entering the cellar, they find the victim unconscious and the culprit is arrested.