Conan figured out from accounts of the missing girl's trip to a convenience store that she was secretly feeding some kittens at some unoccupied building. But when they found the kittens, the girl was nowhere to be seen, and there were clues to a recent motor accident nearby. Traffic police Yumi came and rendered help to the kids.

After locating the girlfriend's car in the mountains with her dead inside, the police suspect it is a suicide following the quarrel. Conan believes the boyfriend is guilty, but needs proof.