A bronze token with "Chang'an" engraved on it, and a rift in time and space shattered by thunder, Xu Xiao, a doctor of literature, fell from a modern laboratory into the cold waves of Qujiang in the prosperous Tang Dynasty.
Dressed in strange clothes and armed with thousands of years of knowledge, he became a homeless "rogue". Fortunately, he was appreciated by Li Jingxuan, the Minister of Civil Affairs, and he stayed in the Minister's Mansion as an aide. While studying the poems and strategies of the imperial examinations in the Tang Dynasty, he carefully concealed the secret of time travel.
In the apricot garden by the Qujiang Pool, a sad piano music brings out the bonds of this life - Shen Luoyan, a talented girl whose family has fallen into decline, is gentle, transparent, and brilliant, and she falls in love with Xu Xiao at first sight. They talked about poetry and paintings, strolled under the moonlight in Chang'an, and their love quietly grew in the splendor of the prosperous Tang Dynasty, but they didn't know that the secret arrow in the court had already been aimed at them. The frame-up of Prime Minister Li Yifu put him in jail and became an imperial prisoner; at the time of separation between life and death, Shen Luoyan's perseverance became his only light.
In exile in the south of the Yangtze River, he used his pen as a blade, made friends with Wang Bo and other celebrities based on his talent and reputation, and collected evidence of crimes, just to clear his name and return home; when he returned to Chang'an, he was named on the gold medal list, paraded around the streets as champion, and married his true love with great splendor, but he was involved in the huge waves of Wu Zetian's usurpation of the Tang Dynasty.
From a lonely and helpless time traveler to the powerful Duke Wu; from the first encounter in Qujiang with the dependence of life and death, from the whirlpool in the court to the revolt to restore the Tang Dynasty, Xu Xiao used his thousand years of knowledge to compete in the prosperous Tang Dynasty, and devoted his life to lovingly guarding the White-headed Covenant.
Under the moonlight of Chang'an, his obsession across time and space is hidden, and he also witnesses an unparalleled love that has gone through prison, exile, and war but is indestructible. When modern souls collide with the spirit of the prosperous Tang Dynasty, when the love of children is intertwined with the righteousness of family and country, this encounter that spans thousands of years will eventually leave the most touching echo in the long river of history.