During the Shaoxing period of the Southern Song Dynasty, in an inconspicuous inn at Mingzhou Wharf, Mr. Shen Ji, the accountant, fiddled with his abacus every day to check the cargo lists of ships passing by. No one knows that he is the sixth batch of "loose civilians" from the Tingtao Bureau, a secret agent agency whose traces have been completely wiped out in history books.
When the first official grain ship turned into "spontaneous combustion" ashes in the night, Shen Ji found a very unusual red copper chisel mark in the wreckage at the bottom of the ship. Following the millimeter-level numerical deviations in the account books, he dug out a code network woven by the Jin Kingdom using inferior copper coins: every adulterated copper coin was a coded beacon for the enemy in the Southern Song Dynasty.
However, the interior of Tingtao Bureau is not clean. The courier delivers false information, the shopkeeper Aunt Yan has her own maritime alliance, Jin Kingdom businessman Wan Yanduo provides clues while demanding blood rewards, and even Shen Ji himself, in the eyes of the "nobleman" in Lin'an, is just a piece of robbery on the chessboard that can be discarded at any time.
When the final secret order was delivered to Mingzhou, Shen Ji discovered that Tingtao Bureau itself was the biggest Bureau. What is cast in the copper coins is not a code, but a verdict of useless chess.
What he wants to do is not to regain the trust of the court, but to find a way out for himself in this dead situation where everyone is at the mercy of the wind.
