Xiao Heng, the seventh prince of Great Xia, guarded the border for ten years, yet suffered a miserable death under a cup of poisoned wine. Reborn back to three years prior, he plans every step, borrows a knife to kill, and forms a "dangerous alliance" with Su Wanqing, an undercover agent deep in the palace. But when they join forces to overthrow the crown prince and pacify the second prince, they discover that the one truly playing the game has never been them. It is the emperor sitting high upon the dragon throne, smiling as he watches his sons fight. A preset death trap, an imperial edict bearing "cannot ascend the throne", a secret tunnel leading to the imperial palace, everyone is a chess piece, and the avenger ultimately becomes the new emperor.