Li Huiyan (Duan Yihong), a Beijing criminal policeman, came to Shuangta, a small city in the northeast, because of a kidnapping case. By chance, he met Zhou You (Dapeng), a mortician who came to find out the truth about his father's murder. The two were accidentally involved in a grudge spanning 26 years... The night fell and the day was covered. In a frozen city standing in the north, twelve days and nights revealed a secret about human nature to the audience. The "double investigation" was reborn in the human nature under the freezing cold...