Kenichi Takabe (Kōji Yakusho) is an emotionally repressed police detective with a mentally unstable wife. Takabe investigates a series of bizarre murders in which each victim is killed in the same way, with a large "X" carved into their neck, but the perpetrator is different each time. In every case the murderers are caught close to the scene of the crime, and although they readily confess to committing the crimes, they never have a substantial motive and cannot explain what drove them to kill.