In 1939, in order to combat the Wang Puppet Government's spy organization No. 76, the Military Control Commission established the Xin'an Special Training Class. Chen Kehai and Fang Li, who were childhood friends, went there together in the hope of fighting against Japan and saving the country. The cruel experience of the special training class made Chen Kehai see the true face of the Military Control Commission. The last assassination mission failed, and Chen and Fang went their separate ways. Two years later, Chen Kehai, who had secretly joined the Communist Party, returned to Shanghai and sneaked into No. 76 undercover. He found that Fang Li had become the director of No. 76, and the two brothers embarked on completely different life paths. Faced with Chen Kehai's personality change, Fang Li repeatedly tried to test him, and even placed the female spy Luo Bing next to Chen Kehai. Chen Kehai was in the enemy camp, surrounded by tigers and wolves. Facing repeated tests and crises, he was fearless in the face of danger. Under the leadership of the party organization, he turned danger into safety again and again, and delivered valuable intelligence to our party. At the same time, Chen Kehai's actions pushed Fang Li's suspicion to the extreme. After the end of the Anti-Japanese War, this pair of former classmates and confidants will have a final showdown for each other's beliefs.