Can Detective Conan crack the case…while trapped in a kid’s body?

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.

It's summer! Conan and Rachel are invited to Serena's family beach house. Serena's sister has a fiancé with a family beach house next door, who plans to introduce his bride-to-be to his father and brothers that weekend. But plans go awry when Conan witnesses the fiancé killing his father! To add to the confusion, it turns out the suspected murderer is one of three identical triplets! Can Conan figure out who the real murderer is? Is this marriage over before it even begins?