The Shadow of Swordsman: Deadly Secret.

August 618 AD. The four prison doors in Chang'an City were opened. As a minister, Li Shimin led his brothers to arrest prisoners on death row overnight. Li Jiancheng, Li Yuanji and He Ruolan showed up. The two colluded with the Lingnan He family and wanted to get rid of Li Shimin. Li Yufeng showed up to save Li Shimin. All of this is Li Shimin's plan to instigate a mysterious case of divine punishment.