In early 1931, Guan Yuda (later known as Han Shan), a business genius who accidentally became a spy, was hunted down and separated from his newlywed wife (Zuo Xiaoqing), so he infiltrated the Japanese secret service under a pseudonym. He reunited with his wife, but they were unable to recognize each other because of his mission. When the military spy Fang Kun (Wu Gang) fell in love with his wife, he was in great pain. In the choice between great love and small love, this CCP agent fought a desperate battle with the enemy with amazing perseverance and extraordinary wisdom. On the eve of victory, he exchanged his blood for the understanding and forgiveness of his relatives.