Programmer Li Zheng no longer believed in love due to a breakup, but he accidentally fell from the Huaqing Pool Observation Deck while his company was traveling in Xi'an, and traveled through time to become the favorite son of Emperor Xuanzong of the Tang Dynasty, the longevity king Li Xuan (historically known as Li Mao). He is familiar with history and knows that he has become the "number one cuckold in history" and will lose his wife Yang Yuhuan to his father Li Longji in the future. He tried to use his prophetic advantage to change his destiny, save the three princes who were framed by Concubine Wu Hui, and prevent the Anshi Rebellion, but he repeatedly failed due to historical inertia. Although Concubine Wu Hui killed the prince and others, she was frightened to death; Yang Yuhuan finally entered the palace, had an affair with An Lushan, and was eventually hanged to death on Maweipo. Li Xuan could only endure and protect herself, but fortunately, Li Mengzhen, a descendant of the former deposed prince Li Jiancheng, came to help him by pretending to be the "princess" he married. The two used each other to gradually develop a true love. He witnessed Prince Li Heng launching a coup and forcing the palace to take power, and saw Li Longji being placed under house arrest until he died of loneliness. Li Heng persuaded him to escape before his death. He and Li Mengzhen faked a fire to escape. On the way to seclusion, they passed by Huaqing Pool. Li Jiancheng's descendants suddenly appeared and forced him to seize the throne. In the chaos, Li Chan fell from the high platform. When he woke up again, he was lying back in a modern hospital, and the nurse taking care of him at the bedside actually looked exactly like Li Mengzhen...
