Detectives from the present and a detective from the past communicate via walkie-talkie to solve a long-time unsolved case.

A drama about the race between people who want to get closer to the truth and those who want to cover it up. Jang Seung Jo will take on the role of Oh Ji Hyuk, an elite detective of nine years who does not share his feelings with others due to pain he experienced when he was young. He is not swayed by money and power, even with the huge wealth he inherited from his uncle.

Detective Squad Chief Choi is set for a promotion. He has a party with his co-workers to celebrate, but, on the way home, a crime occurs and he accidentally commits murder. Because of his promotion, he decides to cover up the crime. The next morning, TV news reveals a body is hanging from a crane at a construction site. Choi is shocked because the body hanging is the person he killed last night. He takes charge of the murder investigation.

As a North Korean sleeper cell agent, Ryu-han infiltrates the South and assumes the role of a village idiot in a rural town. He observes the townsfolk and waits patiently for his mission. One day, after 2 years of playing the role of the village idiot, fellow elite spies Hae-rang, posed as a rock star and Hae-jin, posed as an ordinary student, are dispatched to the same town as Ryu-han. He helps the other two spies settle in and teach them how to adjust in the South. There is a sudden drastic political power shift in the North and all three spies receive an urgent and ultimate mission.