After Lin Miaomiao, a university student majoring in business administration, suddenly dies, she transmigrates into the body of an impoverished orphan girl burdened with enormous debts in the Great Yan Dynasty. Prince Jing, Xiao Jingheng, uses her younger brother as leverage to force her into the imperial harem as his pawn. However, on her very first day in the palace, Emperor Xiao Jingyan sees through the copy of 'Key Points for Surviving in the Imperial Harem' hidden in her sleeve. From then on, Lin Miaomiao gathers intelligence for Prince Jing while using her modern way of thinking to survive in the cracks of the imperial harem. Facing Consort Shu's schemes, the Empress Dowager's manipulation, Noble Lady Ning's secrets, and Prince Jing's ambitions, she gradually learns to strategize, strike back, and weigh her options. But when she finally reaches the pinnacle of power, she discovers that the person reflected in the mirror is no longer the Lin Miaomiao who once believed in sincerity.