The 815·massive murder case 12 years ago broke up his beautiful family and made him an orphan. Over the past 12 years, that strange mask has become his constant nightmare. Twelve years later, with his reasoning ability and subtle insight beyond ordinary people, he became the well-known "Mask Detective" of the Municipal Public Security Bureau. Lost because of the mask, reborn because of the mask. Can he tear off the mask from 12 years ago?