When Chen Xu, a graduate student in the Department of Modern History, was sorting out documents from the Tang Dynasty in the library, he accidentally passed through the spirit of a Chang'an County official who had just died of illness in the first year of Kaiyuan. Faced with a completely unfamiliar household registration system and bureaucratic system, he had to rely on the historical materials of the Tang Dynasty and modern logic in his memory to step by step impersonate his identity, pass the imperial examination, and enter the officialdom. From mediating shop disputes in the West Market to improving water transportation and loading and unloading laws, from being ostracized for his "deviant" academic methods in Taixue, to fighting against all opinions to strengthen the Tongguan defense line before the Anshi Rebellion, he always walked in the gaps of history with the sobriety of a bystander - while trying to improve people's livelihood with modern thinking, he also had to compromise with the unspoken rules of the Tang Dynasty bureaucracy.
