During the Republican era, a river is haunted by inexplicable occurrences. Dun De You is a policeman who succeeds his master 'Old River God,' inheriting his ability to weed out the guilty whenever he lights the pipe. He ends up being suspected for the murder of a distinguished chairman whose son Ding Mao joins hands with him to uncover the truth. Together with some unlikely partners, they begin an investigation that leads them to an incident twenty years ago.