In the last years of the Dayan Dynasty, the post roads were deserted and bandits were rampant. The once-famous "Zhenyuan Escort Agency" fell apart after a murderous escort case, leaving only a few old people hanging on. The protagonist receives a seemingly ordinary letter from home. The pay is very small, but it must be sent from the abandoned city in the north to the Jiangnan County thousands of miles away. Along the way, people from all walks of life are chasing this letter: the government, the salt gang, the old bodyguards, and the refugee leaders. Everyone says it is just a letter, but everyone does not believe it is just a letter. What really affects everyone is not just the content of the letter, but the fact that it can bring an old case that has been buried for many years to the sun again.
