Longyuan City is a strange and beautiful city where steam gears interlock with neon phantoms. On the eve of the annual "Weapons Competition", top players died suddenly due to meltdown of their prosthetics one after another. The scene was as perfect as a crime manual. Shen Yan, the most inconspicuous coworker in the yamen, relied on his unique post-mortem skills and the ability of "criminal retrospection" of unknown origins to sniff out the cold traces of human tampering from the mechanical wreckage. When he teamed up with Ling Qianji, the chief mechanic who was obsessed with motor oil and red oil, the gears of the truth began to turn in the opposite direction - they were tracking not only a serial killer, but also a city memory that had been cleaned repeatedly, an immortality scam using millions of creatures as batteries. In this era where the truth itself can become a murder weapon, Shen Yan's every deduction is approaching a choice: whether to lift the dark curtain shrouding the city, or let himself become the curtain itself to carry those souls who have nowhere to rest.
