In the late autumn of 1941, there was an undercurrent in the French Concession in Shanghai. Tang Anlan, the owner of the cheongsam shop, and Xiao Nianke, the messenger of information, used their daily life as a cover to lurk under the eyes of the enemy. When an urgent secret order from the military commander arrives, the two have three days to obtain the core drawings of the Japanese army's "Amethyst Project" - this germ bomb conspiracy document that concerns the lives of the people in Suzhou River is actually hidden in the gilded pocket watch of Zhou Mingyuan, a spy of the puppet regime. Paramount's birthday party has become a key battlefield, with anesthesia needles, silenced guns, and ventilation ducts for escape, and the crisis is approaching step by step. The hidden compartment of the cheongsam hides the film, and the silver lighter saves the day. They fight side by side in the hail of bullets, and they hide the deep love of comrades that spans three years. The promise of red cheongsam is the hope they hold on to in the darkness and their persistent expectation for victory in the war of resistance.
