The NIS, which has not progressed in the investigation after the assassination of the US president three years ago, is under pressure to hand over the US investigation authority. Meanwhile, Lee Yeon-woo, who was a South Korean operative, requests for personal protection, and the case takes a new turn. Is 'Li Yeon-woo' a decisive witness or a suspect in the case? The truth of the incident is gradually revealed as 'Ryu Seong', a former special forces special forces unit specializing in terrorism, protects 'Li Yeon-woo', whose identity and purpose cannot be grasped..