In the autumn of the second year of Zhenguan, archaeology graduate student Li Yan is transmigrated to the early Tang dynasty when an explosion rocks his laboratory, awakening in the body of Li Chengsi, an orphan from a poor family. The original owner was thrown into prison for secretly possessing fragments of oracle-bone inscriptions from a previous dynasty. After taking over the body, Li Yan uses modern chemistry to identify sulfur and iron ore in the fragments, helping the county magistrate crack an illegal mining case. This earns him a position as an aide to Yun Ye, an official in Chang’an’s Ministry of Works.
Li Yan discovers that this Tang dynasty hides many secrets. The patterns on a Turkic wolf-fang pendant match those on Empress Wude’s jade pendant, forming a star chart. The murals in the underground palace of Emperor Taizong’s mausoleum even contain miniature drawings of a steam engine. Using The Exploitation of the Works of Nature as a model, he improves the curved-shaft plow and boosts grain yields in the Guanzhong region by thirty percent, only to be impeached by the aristocratic clans for “violating the rites.” To clear his name, Li Yan recreates Zhuge Liang’s repeating crossbow at a night banquet in the Taiji Palace. But this triggers a lodestone mechanism in the wolf-fang pendant, exposing a hidden truth about the Xuanwu Gate Incident twenty years earlier: the notch in Li Shimin’s sword perfectly matches traces of titanium alloy powder left in Li Yan’s laboratory.
As the investigation deepens, Li Yan realizes that the fragment of the Analects in the original owner’s memories is actually a codebook, recording advanced technology discovered by Li Jing during his northern campaign. When Li Yan tries to use electrolysis to refine copper ore, he is ambushed by the Guanlong faction. During his escape, he encounters Princess Pingyang, who has been living among the common people. Together, they decipher the star-chart code on the wolf-fang pendant and discover that the underground palace of Emperor Taizong’s mausoleum houses an armillary sphere built by the first Imperial Astronomer. Li Yan’s transmigration may even be connected to the celestial phenomenon “Mars Guarding the Heart,” observed by the occultist Li Chunfeng thirty years earlier...
