A blood contract connects the present and the past. When Chen Yan, a consultant in the modern police station, accidentally exchanged time and space with Shen Yanqiu, a spy from the Republic of China, they discovered that bizarre murders that were separated by a hundred years actually pointed to the same conspiracy. The twin soul array has been activated, and they have become the only keys to each other's world. Caught between two eras, they must work together to prevent the souls of the dead from passing through and the annihilation of living souls.
