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.
Digging for clams at the beach, the Junior Detective League digs up a mystery instead. Did a depressed beachgoer commit suicide, or was he murdered by one of his friends? Then detective Richard Moore faces a challenge beyond his crime-fighting abilities: taking care of his ex-wife’s new kitten! But the pesky furball leads him to the clues he needs to solve an impenetrable code. Could there be a new detective in town—one even cuter than Conan?