Yu Nie is a university student who transmigrated sixteen years ago into the body of a abandoned infant in the fictional Northern Ye dynasty, a chaotic era on the brink of war. Raised by the stern Taoist nun Cui Miaochang at the impoverished Lingbao Temple, Yu Nie possesses modern scientific knowledge but struggles to apply it in this ancient world. Her primary obsession is refining saltpeter to create gunpowder, a desperate attempt to secure a weapon for survival in the coming turmoil. She lives a quiet life with her senior sister Langxi and mute junior brother Ah Hui, performing rituals and temple duties while secretly plotting her escape from the backward county of Huaiyuan.
The story shifts when Ah Hui discovers a bloodied man, Xie Cheng, at the back mountain. He is a guard for the infamous and historically reviled treacherous minister Huan Xun. Yu Nie recognizes the danger, knowing Huan Xun is a ruthless villain who will eventually destroy the empire, but she is bound by temple rules and the law of collective punishment to protect him. The situation escalates when bandits and Rouran invaders attack the temple. During the chaos, Xie Cheng, despite his severe wounds, awakens and kills a bandit. He is then rescued by Huan Zijing, a young cavalry captain who appears to be the true commander of the Xuan Ce Army. Yu Nie initially mistakes Zijing for the villain Huan Xun due to a forged badge, but soon realizes Zijing is an undercover operative investigating corruption.
Huan Zijing stays at Lingbao Temple under the guise of offering an Everlasting Lamp for his fallen soldiers. In reality, he is using the temple as a base to uncover a treasonous plot involving the local magistrate, He Renzhi, who is colluding with the Rouran. Zijing is cold, calculating, and dangerously intelligent, contrasting sharply with the gentle demeanor he presents to the temple residents. He suspects that a higher-ranking official, possibly the Prefect of Dingzhou, is the true mastermind behind the smuggling of military supplies to the enemy tribes.
Yu Nie finds herself entangled in Zijing’s investigation. She attempts to avoid him, fearing the wrath of the historical villain, but is forced into close proximity due to her duties. A comedic misunderstanding occurs when she falls and grabs Zijing’s belt, leading to an awkward exchange that highlights her clumsiness and his amused detachment. Meanwhile, Yu Nie continues her scientific experiments, realizing that the pigment for peacock blue porcelain requires materials she can find in the temple, such as wood ash and alum. She also notices Zijing’s hunting falcon, seeing potential value in its feathers or droppings for her chemical processes.
The core conflict revolves around Yu Nie’s desire to survive and leave the chaotic region versus her growing involvement in the political intrigue surrounding Zijing. As Zijing gathers evidence against the corrupt officials, the threat to the temple increases. The Rouran attack was not a random event but a staged distraction to cover up the treason. Yu Nie must navigate the dangerous waters of the Northern Ye court while continuing her quest for gunpowder, all under the watchful eyes of a man who is both a savior and a potential destroyer of the world she knows.
