Lin Xinxin travels through time to ancient times and is admitted into the imperial harem by the emperor after correctly answering a secret code. Believing she has finally met someone from her own time, she initially thinks she has struck gold. But as they spend more time together, she notices numerous suspicious details. After investigating in secret, she discovers that the emperor has stolen another time-traveling woman's knowledge and achievements, and that he is ruthless in eliminating anyone who threatens him. Trapped in a dangerous imperial palace, she pretends to play along while joining forces with like-minded allies to gather evidence and carefully devise a plan, setting the stage for a battle of wits deep within the palace.