In the midnight chimes of Chang'an, secrets lurk stranger than moonlight. Chen Shi, a junior officer in the Imperial Guard, finds half of a bronze belt plaque while on patrol, unaware that it is a token of the Night Watch Office, destroyed a century ago. When he encounters Aisha, a Persian dancer disguised as a man, using an astrolabe to pinpoint demonic energy in the Ghost Market, and witnesses the blind scholar Shen Mo calculate the time of a murder with an abacus, he realizes the three of them have been brought together by the plaque fragments to form an investigative team:
- **Chen Shi**: A mere mortal on the surface, afraid of ghosts, yet able to crush a zombie's neck with his bare hands. The jade pendant at his waist always grows hot when ghosts appear. It holds the memories of his erased past as a demon-slayer.
- **Aisha**: A foreign princess fleeing with twelve gilded mirrors. The throne stolen by her brother is sealed inside them, and when her astrolabe turns, she can see the last ten breaths of the dead.
- **Shen Mo**: A blind diviner who can calculate the secrets of heaven but not his own fate. Every time he moves a bead on his abacus, he coughs up blood, because he traded his sight for the power to see through Chang'an's ley lines.
Following the clues from the plaque, the three venture deep into the abandoned palace. Beneath the collapsed Xuanwu Gate, they discover a bloodstained stele engraved with hundreds of surnames. A century ago, the Night Watch Office had sacrificed the birth dates of every resident of the city to suppress a demonic tide. When Aisha's astrolabe reveals the truth about Chen Shi's jade pendant, Shen Mo's abacus suddenly catches on its final bead. “The next sacrifice... is us.” Chang'an's night is as dark as ink. The three, bound together by fate, stand back-to-back before the bloodstained stele as the bronze fragments at their waists begin to burn. They are both the ones who can break the deadlock and the final pieces in this sinister game of chess.
