Riko and her friends go to the Kamihama Museum to do a report for their spring vacation project. At the museum, there is a lot of talk about a cat-related incident where a stone statue of a cat held in the Ancient Egyptian Treasures exhibition starts moving at night. Riko and her friends hear about it from the police officers, Ozeki and Komusubi, who are investigating the case, and sneak into the museum at night to find out the truth behind the trouble.