Supermarket Beikado employee Kanzaki receives death threats over the phone. He hires Kogoro to investigate the threats, but Kogoro believes it to be a prank played by a friend. However, an incident occurs the following day on Sunday...

Conan asks Haibara to give him information about Rum, the new Black Organization member who is on the move. She says she doesn't know much about him, but she knows that the descriptions about Rum are always different. Some people say Rum looks feminine, others say he looks like a well-built man, and some other people describe him as an old man. However, there is a common characteristic about him that she can't recall. It turns out that the Detective Boys end up involved in a case again and the three suspects fit each one of the descriptions about Rum.