Kogoro is invited to Yoko's engagement--no, Yoko's friend's engagement with a famous actor. When Kogoro arrives, though, he is hit with a tennis racket by mistake! It turned out that Yoko's frind had been blackmailed by an unknown person, and had bee... (more)n very careful when opening doors since. While everyone is watching a video, Yoko's friend goes showering. After quite a time Conan realises that something must be wrong and goes into the bathroom to find Yoko's friend lying in the bathtub with her neck cut.