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...