During the prosperous Tang Dynasty, bounty hunter Liu Ruyan (also known as Mo Ying), who carries the burden of her family's massacre, encounters the seemingly frivolous Li Xiaoyao while investigating the true culprit. Unbeknownst to her, Li Xiaoyao is actually the reclusive master "Lord Nightwalker," who secretly protects Liu Ruyan. From mutual suspicion to budding affection, the two eventually join forces to become righteous partners, roaming the martial world to uphold justice.