In the year 1941, Nazi Germany declares war against the Soviet Union. Given that Manchukuo's loyalties lie with Cheng Tian, the Russians are caught in a situation where they face threats on all sides. Their intelligence agency devises a long-term plan in secret. Communist spy Tang Fei (Liu Yunlong) receives a mission to infiltrate the enemy by pretending to be one of their own. At the Security Bureau, he crosses paths with Cai Meng (Han Chae Young), a woman determined to fight against the Japanese regime. They gain each other's trust as they try to outsmart the enemy within their own territory.