Jimmy Kudo, the son of a world-renowned mystery writer, is a high school detective who has cracked the most baffling of cases. One day while on a date with his childhood friend Rachel Moore, Jimmy observes a pair of men in black involved in some shady business. The men capture Jimmy and give him a poisonous substance to rub out their witness. But instead of killing him, it turns him into a little kid! Jimmy takes on the pseudonym Conan Edogawa and continues to solve all the difficult cases that come his way. All the while, he's looking for the men in black and the mysterious organization they're with in order to find a cure for his miniature malady.

A diplomat is found dead in his study and Conan's on the case. But what exactly happened? The elder statesman was definitely murdered, but the door and windows to his private chamber were all locked from the inside. How in the world did the killer escape?

And, as if that wasn't bad enough, Conan and his pals get swept up in a missing person caper at the local library. Murder, kidnapping and drug smuggling aren't exactly the sorts of things condoned by librarians. What's the connection? Conan thinks he knows the answer but he's got more pressing things to worry about--like escaping the deadly grasp of the fiendish miscreant!