<검은 태양> 세계의 과거 사건을 그린 그리는 2부작 스핀오프 시리즈. 1년 전 한지혁만 살아 돌아온 작전에서 연인을 잃은 서수연과 차갑고 잔인한 블랙 요원 장천우, 해외파트 담당자 도진숙의 관계와, 이들의 현재에 큰 영향을 미친 4년 전 그 사건이 드러난다.
Su Yeon is a former journalist and a current National Intelligence Service Agent. Chun Woo is an agent with the Foreign Intelligence Bureau where Jin Sook works as a deputy commissioner. The three of them each have their stories and secrets. Su Yeon, who used to be a cheerful and brave woman, closes herself off and takes a dark turn after her lover dies a year before. After she joins the NIS, Su Yeon faces various incidents. There is also a secret behind Su Yeon's past relationship with Chun Woo, the seemingly perfect and cold-hearted black agent. A case from four years ago is revealed, involving Jin Sook, the woman who managed to keep her position as the head of the Foreign Intelligence Bureau amidst power struggles, other female agents, as well as Su Yeon and Chun Woo.