In the ninth year of Wude in the Tang Dynasty, the battle for the right to inherit the throne between Prince Jiancheng and King Shimin of Qin has reached a fever pitch. Li Xuan, a modern history student, accidentally traveled through time and became the twin brother of Prince Li Jiancheng and the King of Qi, Li Yuanji. However, there was a "future memory" in his mind that did not belong to him - he "predicted" that he and his brother would be shot dead by King Qin at Xuanwu Gate, and that King Qi's palace would be bloodbathed. Once this fatal secret is exposed, he will be immediately regarded as a monster by the King of Qin and killed, or he will be executed under suspicion by the prince. Li Xuan faced a dilemma: should he follow history, join Li Shimin, who was destined to win, and betray his blood relatives in order to survive? Or use the prophet to help the prince change his destiny against heaven, but may it cause an even greater historical catastrophe? He chose the third path - to maneuver between the two camps as the King of Qi, secretly accumulating strength. He used the prophet to defuse several assassinations of the prince and win his trust; he also "inadvertently" leaked key information to the King of Qin to show his loyalty. He walks on the edge of the opposing camps, walking on thin ice.
