The Spy: Undercover Operation: Chul-soo is one of Korea’s best intelligence agents: he can accomplish any given mission. One day, a mysterious explosion takes place in Seoul. Chul-soo flies to Thailand on a mission to rescue a person who holds clues to the incident. Meanwhile, Young-hee goes on a business trip to Thailand and gets entangled with Chul-soo’s mission. Will he accomplish his mission and save his wife at the same time?