Lin Shu's whole family was murdered overnight. The crime scene was a secret room with locked doors and windows, and the murderer disappeared. Lin Shu went home to pack his belongings and accidentally awakened the "alarm system", which can sense the distance of the murderer. As the police investigation deepened, the thief Hou Xiaoqiang, his aunt Lin Shufen, and the furniture factory owner Wang Tao were successively involved in the suspicion. Lin Shu relied on the system to find out the real murderer, but the murderer surprised everyone
