During the Anti-Japanese War, Hua Zhen, who was born into a family of high-ranking Kuomintang officials, was originally going to join the navy to realize his dream of becoming a captain. However, an unexpected trip to Shanghai completely changed Hua Zhen's life - he changed his name to Xiang Yuansheng and became a low-level police officer in a run-down police station. Here, Xiang Yuansheng met the two most important people in his life - Communist Party members Chen Hao and Luo Minmin, who helped Xiang Yuansheng find the meaning of life. Under the influence of Chen Hao, Luo Minmin and others, Xiang Yuansheng strengthened his belief in communism and eventually became an excellent fighter on the party's hidden front, fulfilling his pursuit of ideals and beliefs.