The criminal library, dubbed the “Red Museum”, is a police facility that stores the investigation materials and evidence of major crimes where the statute of limitations has run out. Its director Saeko Hiiro is impassive and not good at communicating with people. One day, Satoshi Terada of the Tokyo Metropolitan Police Department’s First Investigative Division is assigned to be Saeko’s subordinate. Although he is bewildered by Saeko’s dispassionate demeanor, Terada starts to organize the data which is the primary responsibility of the museum. He encounters a traffic accident on the way to collect evidence. A truck has hit someone. When Terada rushes over, the victim utters the mysterious words “25 years ago… murder swap” and breathes his last. Once Saeko hears this, she declares a reinvestigation.