A girl named Funako Nakai came to Mouri Detective Agency asking for help of someone named Kazuma Hikone.

One morning, the Detective Boys are on their way to an abandoned building lot which Professor Agasa has managed to loan from a wealthy acquaintance, in order to practice their soccer skills for an upcoming school match. The lot is located next to an eight-story building, and was formerly the site of a mansion which is already torn down, with only a family-sized pool and a shed remaining. However, when they arrive at the lot, they find the grounds crowded by the police: A body has been found in the pool.