Agasa, Haibara, Conan, Ayumi, Mitsuhiko, and Genta go camping. While they're camping they find a lantern in a pond with some writing inside. They show the stone lantern to Conan who determines that it is a code to finding a large diamond. The lantern is also hiding another secret...a dead body at the bottom of the pond. After searching the body they find out that he was a treasure hunter who was straggled to death by another person looking for the treasure. They also find a tear-shaped stone with the kanji "inflammation" written on it and a notebook. The notebook suggests that he was murdered by his partner and that Kaitou Kid is also seeking the treasure. Dr. Agasa goes back to camp to call the police.