Yu Che unexpectedly travels through time and becomes a low-profile shadow guard in the Prince of Duan's mansion. To obtain her freedom, she must complete three years of guard duty and ensure Prince Duan, Qi Xiao, remains safe. Facing assassinations, traps, and political crises at court, she repeatedly turns danger into safety thanks to her special abilities, but in doing so, she also reveals that there is something unusual about her. Qi Xiao gradually moves from suspicion to trust and joins forces with her to uncover the conspiracy behind everything. As the three-year deadline approaches, Yu Che believes she can finally walk away unscathed, only to discover that their years fighting side by side have already forged an unbreakable bond between them.