For an astronomical observation, conan and the group went to this pension deep inside the mountain. Other than the pension owner, there were also other three people in the pension, the victim's fiancee and the two magazine staff. As they went to the nearby hill to see the stars, they saw a decayed bones and on top of it they found the dying message and then that night the other man from the magazine staff was killed and left another dying message.

The Detective Boys are on a camping trip accompanied by Ran. Later they witness an arguing couple who then leaves. They then set up the tent in the couple's area. Later, the couple returns demanding their place back and the girlfriend decides to let them have it. Later Ran is drugged and kidnapped. The kidnapper is later found in another car in a road accident. Conan reveals the boyfriend hired the kidnapper to murder his girlfriend, but captured Ran instead because of their tent placement. After examining some clues, he realizes that Ran is in a river and that the it will flood at 3o'clock. After saving Ran, everyone becomes exhausted except for Ran who has just woken up from her nap.