Following a failed assassination attempt on the U.S. president three years ago, the National Intelligence Agency, having made little headway in the investigation, faces pressure to transfer the case to the United States. In the midst of this, Lee Yeonu, a former North Korean intelligence agent, seeks protection, propelling the inquiry into a new phase. With his identity and motives unclear, former special forces major Ryu Seong is assigned to protect Lee Yeonu. The central question lingers: is Lee Yeonu a crucial witness or a suspect in this intricate case?