Kogoro and Conan search a fourth floor apartment when they're asked for help by the trio standing in front of the room: Saki's friend Maiko, building manager Yoshie, and deliveryman Matsuda. Inside they find the bodies of residents Maehara and his wife Saki. Day trader Maehara had recently made a lot of money, and the valuables are missing from the apartment. Inspector Megure deduces from the apartment's condition and the testimony of the trio that Saki pretended to be a robber and murdered Maehara, but made a mistake while disguising herself as a victim and suffocated herself. However, Conan notices something strange about the crime scene...

The body of murdered neighborhood nuisance Amagi is discovered, and neighborhood association president Bando also appears to have been poisoned pesticides. The police believe Bando chose to kill himself after murdering Amagi, but...