Spy

Sun Woo, a field agent with the National Intelligence Service, has a mysterious accident while on a mission in China. After returning to Korea, he is assigned to the information analysis team. Hye Rim, a housewife, is completely unaware that her son, Sun Woo, is an agent with the National Intelligence Service. The National Intelligence Service gets tense with a North Korean spy turning herself in. Sun Woo tries to find clues about the accident in China through Soo Yeon, the North Korean spy.

Ki Chul, Hye Rim's former boss, suddenly shows up at her house and threatens to reveal her real identity to the world. Hye Rim cannot tell anyone about her troubles and tries to solve the situation without her family knowing. Meanwhile, Sun Woo gets closer to the identity of the man with a burn scar who killed his partner in China.

Ki Chul keeps pushing Hye Rim to bring Sun Woo to him. However, Hye Rim refuses to bring Sun Woo to him and she eventually decides to turn herself in. While Sun Woo is investigating the subway bombing case, he hears that the case of Soo Yeon, the spy, will be closed with a press conference to announce that she had defected to South Korea.

Sun Woo suggests to Joong Hyuk an operation by using Soo Yeon as a double agent to find out the North Korean spies who came to South Korea. Meanwhile, Ki Chul orders Hye Rim to watch Sun Woo's every move and to report to him. While she is watching Sun Woo, she accidentally learns about the double agent operation.

Sun Woo is shocked by Soo Yeon's death but tries to save her family as promised. Joong Hyuk blames Sun Woo for the failure of the operation and doesn't allow Sun Woo to try to save Soo Yeon's family. Meanwhile, Ki Chul finds out that Hye Rim deleted part of the wiretapping, causing Ki Chul to lose trust in her. Hye Rim tries to stop Ki Chul from getting to Sun Woo.

Hye Rim suspects that Ki Chul has also planted a wiretap at Yun Jin's apartment and sneaks inside there. While Hye Rim is searching if Yun Jin's apartment is bugged, she becomes suspicious of Yun Jin's identity. Meanwhile, Sun Woo gets close to finding out who Ki Chul is while looking for traces that Ki Chul left on the day Soo Yeon died.