The story begins with the arrival of a stoic, mature girl named in Conan’s elementary school class. Initially appearing as just another transfer student, she surprises Conan by revealing her true identity after school: she is Shiho Miyano , a former scientist for the Black Organization code-named Sherry .
The episode concludes with a haunting moment: Haibara breaks down in tears, confronting Conan about why he couldn't save her sister, Akemi, despite his great detective skills. This emotional climax cements Haibara as a permanent, tragic ally in Conan's fight against the Black Organization.
Conan deduces that the "locked" door was a trick involving a cassette tape and a heavy dictionary.