Choi Kang is suspected of being a spy after a clash with a foreigner of unknown nationality. While tracking the foreigner's secrets with Kwak Byung-nam and Lee Yong-hee, he discovers an unexpected clue. This clue connects to Choi Kang's past.

A series of mysterious incidents unfold in Changri-dong. Choi Kang, Kwak Byeong-nam, and Lee Yong-hee begin to investigate the truth behind the incidents. The military attempts to cover up the situation, and someone is quietly watching the whole situation unfold.

A video of Kim In-seop exposing the incident goes viral, but no one raises suspicions. Park Jeong-hwan and Jeong Nam-yeon join Choi Kang, Park Byeong-nam, and Lee Yong-hee to uncover the truth behind the incident, and armed forces kidnap Kim In-seop.