The eldest daughter of Detective Shibasaki Sachio from the First Investigation Division is found stabbed to death. He goes after the truth with Kawasumi Shigekatsu, a junior detective who respects Shibasaki as his mentor in life and is a close family friend. However, the hard work of the police is in vain. There are no developments due to the numerous questionable points at the crime scene and case goes unsolved. 15 years later, Shibasaki is retired and quietly spending the rest of his life looking after his wife Miwako who is seriously ill. However, the situation suddenly changes with the establishment of a unit specialising in re-investigating unsolved cases. Kawasumi also joins them. As the case is being reexamined, the existence of man who is believed to be the criminal emerges.