Blind guqin musician Xu Henian makes a living tuning instruments, but secretly uses the vibrations of his strings to send Morse code to his organization.
Lou Jinting, head of the Wang Jingwei regime's secret service, is obsessed with the guqin. He has hidden an intercepted codebook inside the belly of Jiao Wei, a Ming-dynasty guqin. Xu Henian receives an order: destroy the instrument and retrieve the code within three days. But he discovers a map of a Japanese poison gas factory concealed inside the body of the instrument, intelligence far more deadly than the codebook. He decides to take a gamble: he will use a broken string to fake a crack in the instrument, making Lou Jinting smash it himself.
As Jiao Wei hits the floor and the map slips out from its hidden compartment, Xu Henian hears Lou Jinting's Browning press against the back of his neck.
