After his mother is brutally murdered by the Triad in Thailand, Soo-hyun is adopted by NIS agent Kang Joong-ho, and he grows up with Min-ki like brothers. Min-ki and Soo-hyun both become NIS agents later on. One fateful day, Soo-hyun meets Ji-woo after last seeing her in Thailand when he was a child. They start dating. One day, Soo-hyun ruins a mission when the suppressed memories of the day his mother died surfaces in his mind. NIS Director Jung gives Soo-hyun an undercover assignment to infilt...