At a traffic prison, an inmate's body is found standing at attention. The scene appears to be sealed, and the escape of another prisoner forces the prefectural police to act quickly. The circumstances of traffic accident perpetrators and victims, their families, prison officers, and detectives converge as the case leads to an issue connected with Article 39 of the Japanese Constitution.

A classic mystery in which a seemingly locked-room killing and an escape at a traffic prison bring together the conflicting motives of people affected by traffic accidents.