Conan and his friends come to a lodge and fossil museum in Gunma to go on a fossil finding trip. Journalist Miyashita Umika also arrives at the lodge. She explains that she has come to write a story on the rare moon's droppings fossil that was discovered in the town. Museum owner Ogami and village mayor Nakatani are planning to make the fossil the town's village in order to promote it, but Umika mutters that she hopes it doesn't become a negative symbol. Later, Ogami is interrupted while trying to tell something to Umika, and his dead body is discovered in the bathroom...

A large group of reporters have gathered in front of the Kudo family home. Everyone online is talking about how Shinichi solved the Fighting Red Tengu murder case. Conan decides to hide in Agasa's home until the commotion blows over. Haibara, Genta, Ayumi, and Mitsuhiko are asked by their homeroom teacher Kobayashi to visit Higashio Maria's home after school. Maria should have been at school that day, but she never showed up. Believing Maria most likely went to look for the treasure hidden by her late grandmother, Haibara and friends begin deciphering the treasure hunt clues, but...