Wu Young-min, a former policeman who inadvertently brought about the death of his partner during a faceoff with a criminal, has quit the police force and now heads up security at Dreampia Department Store as an employee of the security company SecuZone. Having been caught up in the situation at the department store, Wu comes across his former rival and co-worker Ha Hyun-su, who now heads the investigation into the recent murders. The presence of Ha and the situation as a whole causes Wu to relive the horrendous memories which he has since tried to forget. Meanwhile, Choi Sang-ki is head of SecuZone, which is hurrying to solve the recent string of murders. A mysterious woman Lee Ji-hyun is also found lingering about the crime scenes. Without wishing it, Wu is drawn farther and farther into the deeping mystery surrounding the murders.