The world has been divided into two halves by a giant wall to prevent the epidemic of "Dark mist". In order to shelter the refugees, artificial cities called "Arks" were built. Shido Enishi is a private detective, who works at the ninth Ark. One day, he is asked to capture a burglar. The seemingly simple case leads him to a great conspiracy. The world has been divided into two halves by a giant wall to prevent the epidemic of "Dark mist". In order to shelter the refugees, artificial cities called "Arks" were built. Shido Enishi is a private detective, who works at the ninth Ark. One day, he is asked to capture a burglar. The seemingly simple case leads him to a great conspiracy.