The story begins when late at night, in a noisy gambling den, a gambler secretly stakes his family's treasured heirloom, the Seven Stars Sword, which is said to have the power to control demons! Shortly after, the apostle of the Divine Moon Sect, the Sichuan Overlord of the Four Heavens, appears out of nowhere, turning the gambling den into chaos and leaving bodies scattered. From that day on, the world of murim is plagued by horrific and brutal incidents. The murim's dedicated arrest agency, Inryeong Unit, is dispatched to the scenes of these mysterious cases. They recognize the emergence of a massive dark force and set out to track its source. Meanwhile, for the sake of her family's revenge, the disguised Hee-yeon joins the Inryeong Unit, but is discovered by the captain, Beom-yeop, on her first day! But for some reason, Beom-yeop allows Hee-yeon to remain in the Inryeong Unit. Can the Inryeong Unit prevent the revival of the Divine Moon Sect, which was thought to have vanished into the legends?!