Detective Conan: The Time Bombed Skyscraper

Once brilliant teenage detective Shinichi Kudo was given a poison that reverted him to a 4-year-old. He's adopted the pseudonym Conan Edogawa so no one (save for an eccentric inventor) will know. Now he's got to solve a series of bombings before his loved ones become victims. Who is this madman and why is he doing this