Conan and the Detective Boys decide to go camping with Professor Agasa and their new member, Ai Haibara. Their plans change however when they find out that Professor Agasa forgot to bring a tent. When they go looking for shelter, they find a castle. The owner of the castle agrees to allow them to spend the night. They are later told that there is a great treasure hidden in the castle. They also discover that there are clues left behind to find this treasure. The Detective Boys feel they have more than enough time to solve this mystery, but when Conan goes missing their time is cut short. Now they must find Conan before he turns up dead.