The woman turns out to be another classmate, previously a male but now a female. After Conan re-examines the hint, he realizes that the sounds were animal noises pronounced by the English. After finding her, she leaves pretending not to know Agasa, believing the Detective Boys were his grandchildren and that she was intruding his happy family. Agasa reveals he knows it is her as she drives away.

Mouri, and Conan are checking out costumes for Mouri's one day of being a chief firemen. Later they meet people attending a costume party. While walking home, they find a police car in front of the house and meet the people from the costume shop earlier, realizing the host has been murdered. Conan realizes that the culprit must've interfered with the Rigor Mortis and finds the evidence to convict the culprit. The culprit reveals that the host was his controlling girlfriend.