My fiancée has returned... as an assassin sent to take my life— A poignant story between Seora, who returns as an assassin, and Heejin, who loves only her with all his heart. Meanwhile, ruthless political strife and intense conspiracies unfold within the imperial palace. From the northern region of the Wi Empire, a sacred decree is issued to Prince Yeon, forcing him to marry Lee Seora, the illegitimate daughter of Minister Lee Yonghyeok. But in truth, Lee Seora is an assassin hired by the Empress, who seeks to keep Yoon Heejin under control. Heejin realizes this almost immediately. However, the two share a deep bond from the past, and Heejin has never been able to forget her. Seora, who lost her memory before the age of twenty and became an assassin, begins to recall fragments of her past, and after confirming their feelings for each other, the two gladly accept their marriage. Even so, they become hopelessly entangled in the imperial family's power struggle, and a fierce political battle for the throne erupts within the Wi Empire.