Detective Yoshioka is investigating the drowning death of a young woman who is wearing a red dress. Face down in a muddy puddle, her stomach is found to be full of sea water. Clues begin to point to the detective as the killer, since his fingerprints and personal items are located at the murder scene. As more bodies turn up that have been killed in the same way, even the detective begins to wonder whether he himself may be the very murderer that he is pursuing.