Modern history scholar Chen Yuan traveled back to Nanjing in 1937 through a family bronze mirror and became a teaching assistant at Jinling University. He found himself at a critical moment on the eve of the Anti-Japanese War, and had intersections with his young grandfather (Zhang Mozhi) and historical figures Xiao Yunfeng and Zhou Yaqin. As the Nanjing Massacre approaches, Chen Yuan tries to use historical knowledge to save his relatives and friends, but is caught in the moral dilemma of changing history and maintaining the timeline. Each use of the bronze mirror accelerates the oxidation of the mirror, suggesting limited opportunities for time travel, while the inscriptions hidden in the mirror and the multiple mirror worlds reveal a huge conspiracy spanning time and space.
