In 1939, the Anti-Japanese War entered a stalemate stage, and undercurrents surged in the Shanghai Concession, known as the "isolated island". Many forces including the Japanese Super High School, the Military Command, the Central Command, Wang Puppet No. 76, The Soviet Far East Intelligence Agency, and the underground party are competing fiercely here. Lin Mo, an ace agent at the Military Command Shanghai Station code-named "Nightingale," accidentally intercepted a top-secret message - "Purple Secret" - about the direction of the European war situation and the Japanese military's major strategic adjustments. However, this action exposed his identity and he was hunted by the enemy. He was seriously injured and lost his memory, but was rescued by a seemingly ordinary dancer Ruan Qingqiu. In the process of searching for the memory fragments and the truth about the "Purple Secret", Lin Mo found himself trapped in a huge vortex of conspiracy. His former comrades became suspicious, people around him had their own secrets, and every step could lead to an abyss. He must distinguish the true from the false when he is lost, fight back in the encirclement and suppression, join hands with the lurking comrade "Fisherman", and pass on this information that may change the balance of war at all costs, and engage in a thrilling battle of intelligence and will on the silent battlefield.
