Watchmaker Zheng Qiran has been repairing watches for twelve years. No one knows his other identity - the last unactivated latent agent in Shanghai, codenamed "Postman". He does not use radio waves, but uses the city's most primitive connections to deliver information.
The sleeper radio station was uncovered and all liaison officers arrested. The first piece of information was hidden in the advertisement in the middle of "The Declaration", the second piece of information was through the rickshaw driver's cut in the street, and the third piece of information was the dance rhythm of the Paramount Ballroom.
But this time, he met a real opponent. Sato Kenichi, a professor of mathematics at Tokyo Imperial University, was ordered to come to Shanghai to take charge of the Japanese military cryptanalysis course. This man wearing thin-rimmed glasses doesn't believe in torture and forced confessions, he believes in mathematics. In his view, the whole of Shanghai is like a huge clock, and all the gears mesh in a regular manner. He calculated step by step along the cigarette butts, footprints, and time difference to remove the "postman" from the fabric of the city.
When the ultimate intelligence "Operation No. 1" Plan surfaced, all the clues were woven into a web - the last step of this web could only be completed by the death of the transmitter himself.
A life-and-death chase between a watch repairman and a mathematician, a secret battle woven with time and pace. He uses the precision of repairing a watch to protect his faith, and he uses the sharpness of formulas to dismantle the truth. Who reaches the finish line first? The answer is hidden in the corner of every alley in Shanghai.
