A poisoned yokan arrives at the office of former minister Todo (Shiro Sano), and his secretary dies after eating it. The giver is arrested, and Sada (Teruyuki Kagawa) takes the case. Meanwhile, Sawatari (Akira Shirai), a former forensic scientist who now uses his own methods to conduct an expert examination, offers to reappraise the poison. Sawatari points out that it is the same as the case from two years ago, and Fukayama (Matsumoto Jun) begins to investigate.