In the winter of 1941, the Underground Communist Party, "Three Scenes of West Lake," is activated to counter the Imperial Japanese Army's biological warfare initiative, Project Slumber. Chen Kailai, an assistant photographer at Chunguang Photo Studio, sets off for Shanghai for a clandestine rendezvous after witnessing the death of his mentor, Li Musheng, an underground operative codenamed Broken Bridge. En route, he gets acquainted with Jinbao, a fugitive dance hostess sharing a similar plight. Aboard the train, they encounter Su Men, a special commissioner of the Wang-controlled puppet regime, and are drawn into the regime's infighting. Arriving in Shanghai, Chen opens a photo studio with Jinbao's assistance to await his contact—unaware that Jinbao is actually an agent, codenamed God of Wealth, under the nationalist military intelligence agency, NBIS. When Shen Kexi, codenamed Su Causeway, finally shows up, Chen hands over his late mentor's belongings to her and participates in underground operations. Witnessing Shen being arrested, Chen assists Zhao Qian, codenamed Leifeng Pagoda, to rescue her successfully. Determined to become a qualified underground agent, Chen takes over the codename Broken Bridge. Together with Su Causeway and Leifeng Pagoda, he carries out perilous tasks under the command of their superior codenamed Diana. Finally, Chen helps Shen sneak into the lab to steal samples, exposing the Japanese atrocities and preventing a viral disaster. However, along the way, Zhao, Shen, and Jinbao are martyred, and Chen records every moving moment with his camera.
