And It'd be Nice If Everybody Disappeared

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.