When nighttime comes, Ai investigates freely and is accompanied by the Detective Boys. They enter the same secret passage as Conan did and wander out of another secret entrance. Genta remains trapped in the passage and captured by the culprit. Mitsuhiko investigates the doorway to the castle's tower and disappears. Ai and Ayumi investigate the abandoned tower of the castle and find the culprit using a secret entrance connected to the castle. They find a corpse and realize who the culprit is pretending to be, the mistress. When Ai and Ayumi were coming out from under a floor tile, the culprit grabs on and tries to kill them. Then Conan, Mitsuhiko, and Genta appear. After re-uniting with the everyone, Conan reveals the location of the treasure. The treasure was the castle, and a beautiful scene. The culprit breaks down realizing that they wasted 10 years and killed a huge number of people just for this. The culprit is captured.