Li Changfeng, a science student, transmigrates into the body of the eldest legitimate grandson of the Prince of Zhennan. After his parents die in battle, he is ostracized and persecuted by his paternal uncles, then banished as a disgraced heir to Canglang County, a bitterly cold frontier fief. Facing a desperate situation, he uses his modern scientific and engineering knowledge to make the most of local resources: building heated kang beds, digging deep wells, refining pure salt, and forging Mo Dao swords. He gathers refugees and establishes a local militia, repeatedly thwarting the oppression of powerful local clans and mountain bandits. He also wins the support of the Northern Frontier Army, becoming its exclusive weapons supplier. Just as his influence begins to take shape, the Northern Rong launch an attack on the border, and beacon fires rise across the land. Using Canglang Fortress as his stronghold, he prepares to embark on a journey of defending the frontier and turning the tables.