After the Korean War ends, Jeong Sa-yong, who went to North Korea alone, barely survives as a laborer at the Pyongyang Grand Theater amidst a purge of those from the South. Meanwhile, with the help of people's actress Choi Yeong-sil and Lee Jeong-seon, he gets married and has a daughter. When Jeong Sa-yong's uncle becomes a powerful member of parliament in South Korea, Jeong Sa-yong visits his uncle as an infiltrated spy from the North. However, Jeong Sa-yong surrenders with his uncle's help and gradually gets used to a new life. Two years later, Kim Gyeong-cheol, an agent of the Central Intelligence Agency, investigates Jeong Sa-yong's mysterious suicide. In the course of the investigation, Kim Gyeong-cheol discovers that Jeong Sa-yong met Lee Jeong-seon by chance during an overseas business trip and secretly exchanged letters with Choi Yeong-sil, his former wife in North Korea. Jeong Sa-yong was not actually dead, but had faked his death to ensure the safety of his beloved wife and daughter. Finally, Kim Gyeong-cheol, upon learning this fact, begins a relentless pursuit as if it were himself.