A CCP undercover Zheng Chaoyang lurks in Peiping police station is informed by a traitor and evacuates immediately with secret list of KMT spies. After the liberation of Peiping, Zheng Chaoyang returns to Peiping to fight KMT spy organization named "Tao Yuan" led by a spy coded "Phoenix" who is actually Chaoyang's brother Zheng Chaoshan.