At long last, Conan has located the scientist responsible for the formula that turned him into a kid, Anita Hailey. Trouble is, she's taken the formula herself--and she can't change back! Together, Conan and the diminutive doctor track down a floppy disk that may contain the secret to curing their condition, only to find the former owner crushed under a fallen bookshelf. Can they crack both the locked-room mystery and the locked disk? Afterward, Heiji invites Conan, Moore and Ran for sightseeing in Osaka. They then meet Kazuha Toyama, Heiji's childhood friend who mistakenly thought that Ran was Heiji's girlfriend. A series of murders have been occurring in Osaka. When Conan and co. find a man guilty of a murder 20 years ago, he tries to stab Ran, but Conan leaps in front of her and thus is stabbed instead. However, he is saved by the lucky charm that Heiji gave him earlier. Elsewhere, Heiji confronts the serial killer. When the murderer tries to commit suicide, Heiji manages to stop him, but is shot in the stomach.