
She married a monster to steal his power—and poison him in his sleep. He saw through her sweetness, slipped into her world, and stayed. In a court built on lies, their alliance is the most dangerous secret of all.

The second daughter of the Shenfeng Marquis Manor, Qin Qianqian, is fiercely opposed to her arranged marriage to the rumored cruel eunuch, the Ninth Thousand Years Old Xiao Xun, due to her affections for another. To protect her family, the eldest legitimate daughter, Qin Wanzhi, volunteers to take her place. She also presents a blueprint for restoring the family's glory through this alliance, earning her father's approval. However, on the wedding night, the substitute bride, Qin Wanzhi, reveals her true intentions in the bridal chamber. She is not sacrificing herself for the family, but harbors deep hatred and plans to harm Xiao Xun, seize his fortune and power, laying the groundwork for future revenge and power struggles.

This episode tells the story of Qin Wanzhi, the legitimate daughter of the Shenfeng Marquisate, who feigns poisoning on her wedding night to test her husband, the Nine Thousand Years Old Xiao Xun, in her bid to seize the secret imperial edict from him. Xiao Xun, who wields immense power in court, had already seen through her scheme. He plays along, simultaneously attempting to sway Qin Wanzhi's murderous intent with generous gifts and care, while also disguising himself as his personal bodyguard "Xiao Liu" to get close to her and investigate her true motives. However, when the two meet under their new identities, Xiao Xun is shocked to discover that his new bride is actually an old acquaintance he knows, adding a new layer of mystery to their relationship.

The episode opens with the male lead, Xiao Xun, being ambushed and poisoned in the wilderness. The female lead, Qin Wanzhi, and her half-sister, Qin Qianqian, discover him on their way to a temple. Qin Wanzhi, with her cunning mind, recognizes Xiao Xun's noble identity. For her future revenge plan, she decides to help him, gives him an antidote, and leaves. Qin Qianqian, who has always been jealous of and wanted to harm her sister, takes the opportunity to stay behind and lies to the awakening Xiao Xun, claiming she saved him. This act successfully deceives Xiao Xun, laying a crucial groundwork for misunderstandings and conflicts between them, leading Xiao Xun to mistakenly believe Qin Wanzhi is the one who wants to harm him.

On Qin Wanzhi's return visit to the Thousand-Year-Old Prince's mansion three days after her wedding, her father Qin Zheng appears warm but is secretly wary of the Prince's power. Her half-sister, Qin Qianqian, feigns closeness, luring Qin Wanzhi back to her room only to turn hostile and demand if the secret of the arranged marriage has been exposed. After confirming her safety, Qin Qianqian presses further, asking Qin Wanzhi to use her identity as the Prince's wife to help her be chosen as the Fourth Prince's consort. Qin Wanzhi deflects by claiming the Prince is gravely ill and not receiving visitors. Enraged, Qin Qianqian attacks her violently. All of this is witnessed by the Thousand-Year-Old Prince Xiao Xun, who is disguised as a guard.

The episode opens with the female protagonist, Qin Wanzhi, being subjected to humiliation and bullying by her stepmother, Su Wan, and half-sister, Qin Qianqian, at her husband's home. At a critical moment, the male protagonist, Xiao Xun, disguised as a guard named "Xiao Liu," steps in to protect her with the authority of the Nine Thousand Years Old's residence. He publicly exposes Su Wan's status as a concubine, causing her to lose face. Qin Wanzhi's father, Qin Zheng, intervenes to mediate, suppressing the situation out of fear of the Nine Thousand Years Old's power. Qin Wanzhi, meanwhile, strengthens her resolve for revenge internally while outwardly maintaining a submissive facade to stabilize the situation. The episode concludes with Qin Wanzhi being startled by an unknown intruder while alone late at night, leaving a cliffhanger.

Maid Qiuju discovers the secret that her mistress, Qin Wanzhi, poisoned the Grand Eunuch, and uses this to blackmail her. Qin Wanzhi feigns compliance on the surface, but decisively acts to silence Qiuju permanently. All of this is observed by the Grand Eunuch (Xiao Xun), who is quite impressed by Qin Wanzhi's ruthless and two-faced methods. Just as the surviving Qiuju attempts to report Qin Wanzhi to the Grand Eunuch, he reveals that he has already uncovered Qiuju's past crimes and coldly sentences her to death on the grounds of "a life for a life."

Xiao Xun (the Nine Thousand Year Old) secretly eliminates Qiu Ju, an informant planted by his wife Qin Wanzhi's stepmother Su Wan, and uses this as a test. Qin Wanzhi, though suspicious, remains cautious. Meanwhile, Su Wan invites Qin Wanzhi back to her mansion under the pretense of returning her birth mother's belongings, intending to set a trap. Qin Wanzhi decides to play along. Upon learning that Qin Wanzhi is doted upon in the Nine Thousand Year Old's residence, Su Wan and her daughter Qin Qianqian, consumed by jealousy over the immense fortune Qin Wanzhi might inherit after the Nine Thousand Year Old's grave illness, begin to plot against Qin Wanzhi, aiming to take her place.

This episode sees protagonist Qin Wanzhi return to the Qin manor, only to be jointly framed by her stepmother Su Wan and stepsister Qin Qianqian. Su Wan and her daughter put on a facade of warm hospitality but secretly drug her tea. Once the drug takes effect, Qin Wanzhi is locked in her room. Outside, Qin Qianqian gloatingly reveals her vicious plot to drug her and bring in a man to ruin her reputation. At Qin Wanzhi's most desperate moment, a ruffian enters the room and pushes her to the brink of life and death, setting the stage for future conflicts and revenge.

She married a monster to steal his power—and poison him in his sleep. He saw through her sweetness, slipped into her world, and stayed. In a court built on lies, their alliance is the most dangerous secret of all.