A group of enchanting Butterfly Servants, like ferocious beasts, infiltrates the city and attacks the commoners. Ling Chang Feng, together with the Ministry of Security and the Imperial Guards, bravely protects the people. However, Tang Qian Yue, who is sent to seek refuge at Fengyue Pavilion, is attacked by Butterfly Servants and left lying in a pool of blood. Startled awake, Tang Qian Yue realizes it is still early on New Year's Day. The nightmare has been so vivid that she nervously lives through this day, which holds great significance to her over the past three years.

Ling Chang Feng found the Butterfly Mark under the captured Butterfly Servant's collarbone. Tang Qian Yue realizes Ling Chang Feng's change in attitude and remembers what happened last night. She pulls her clothes to one side and found the Butterfly Mark on her collarbone as well.

Ling Chang Feng reminisces about his marriage to Tang Qian Yue. At that time, Tang Qian Yue doesn't have any Butterfly Mark on her body, and she is visibly anxious and confused. Why does the vanished Butterfly Mark reappear? Ling Chang Feng deduces that the night raider, based on various characteristics, is a Butterfly Slave who has been infected with the Butterfly Pest of the Yilan Tribe. Once someone becomes a Butterfly Slave, they lose all their mental faculties and become extraordinarily aggressive.

In the prison cell, the Butterfly Slave, who seems to have died, suddenly comes back to life. Ling Chang Jin's guard, Kun Qing, promptly arrives and informs Ministry of Security's guard, Jin Ming, that the Butterfly Slave has merely been feigning death after being wounded by a sharp weapon. To completely kill the Butterfly Slave, the body needs to be burned. Ling Chang Feng stabbed Tang Qian Yue with his sword to momentarily shock her. Upon regaining consciousness, Tang Qian Yue confesses to Ling Chang Feng that she has always been a Butterfly Slave. However, she is different from the others as her mind was still intact.

Tang Qian Yue fears that Ling Chang Feng will abandon her once again, so she stays by his side at all times. Ling Chang Feng has no choice but to bring Tang Qian Yue back home. It is then that Tang Qian Yue finally manages to utter her first words, albeit hesitantly. Ling Chang Feng cares for Tang Qian Yue like a family member, summoning Madam Hong to assist in bathing the dirty Tang Qian Yue and tending to her injured foot with great care.

As days pass, Tang Qian Yue seems to have blended in with the women of the city and grown into a respectable lady. She waits for Ling Chang Feng to come home every night. Reaching the age of marriage, living together with a single man is bound to raise suspicions. Although Tang Qian Yue doesn't mind, she overhears that the commander is urging Ling Chang Feng to fulfill his engagement with the daughter of the prime minister.

In fear of potentially harming Ling Chang Feng, Tang Qian Yue decides to consume Mokui soup to rid herself of the Butterfly Curse. She endures seven days and nights of excruciating pain. During the seven days that Tang Qian Yue is missing, Ling Chang Feng searches the entire city. When he returns home in a state of despair and discovers that Tang Qian Yue has returned, he finally experiences the joy of regaining what was lost and requests that she stay by his side as his wife.

Ling Chang Jin, deeply resentful due to his elder sister's death, holds a grudge against Yilan Butterfly Slaves. With the assistance of Ling Chang Feng, he captures the Yilan Crown Prince, who had plotted the New Year's Eve attack. From the Yilan Crown Prince's confession, Ling Chang Jin learns that Princess Bao Zhu possesses Kirin Blood that can nourish the Butterfly Curse.

Tang Qian Yue realizes she is now afraid of black peonies, the nemesis of the Butterfly Curse, so she asks Madam Yuan for another way to remove the curse again. Meanwhile, Ling Chang Feng learns about the black peonies soup method from the "Book of Curses" and finally knows the reason why Qian Yue was missing. She even had to suffer for three years after the curse is removed in order to stay beside him as a normal person.

Tang Qian Yue is drawn to Bao Zhu's blood and turns into a Butterfly Slave. However, Tang Qian Yue shows up not to harm Bao Zhu but to safeguard her from the assaults by other Butterfly Slaves. Ling Chang Feng manages to temporarily restore Tang Qian Yue to her original state using the black peonies' essential oil, but this incident is witnessed by Ling Chang Jin, leading him to harbor suspicions regarding Tang Qian Yue's true identity.

The commander orders Ling Chang Jin to get rid of all the Butterfly Slaves and not be as soft-hearted as Ling Chang Feng. Ling Chang Jin invites Chang Feng and Qian Yue to his residence for tea to see if Tang Qian Yue is a Butterfly Slave. Chang Feng and Qian Yue are troubled when Chang Jin pours her a cup of black peony tea. Chang Feng has no choice but to leave with Qian Yue.

In an attempt to save the captive Butterfly Slaves, Ling Chang Feng enters the prison cell to assess the condition of the slaves who were fed the black peonies soup. At that very moment, black peony petals drift throughout the city, and when inhaled by the imprisoned slaves, they become restless and eventually turn to ashes. Tang Qian Yue, at this moment, also exhibits peculiar symptoms.

In an attempt to save the captive Butterfly Slaves, Ling Chang Feng enters the prison cell to assess the condition of the slaves who were fed the black peonies soup. At that very moment, black peony petals drift throughout the city, and when inhaled by the imprisoned slaves, they become restless and eventually turn to ashes. Tang Qian Yue, at this moment, also exhibits peculiar symptoms.

Ling Chang Feng watches the unconscious Tang Qian Yue when he suddenly receives a secret message that the Butterfly Slaves in the city have been completely eliminated by the commander. He realizes that the petal shower is unleashed by the commander to eradicate the Butterfly Slaves once and for all.

Princess Bao Zhu avoids sleeping with Marquis Wu An and leaves early with many things to find an opportunity to find Qian Yue. However, she realizes Ling Chang Jin has been following her. Bao Zhu is worried that Ling Chang Jin might find out where Tang Qian Yue is staying so she tries to distract him, but Ling Chang Jin just won't give up.

Ling Chang Jin and Princess Bao Zhu gaze upon the snippets of Ling Chang Feng and Tang Qian Yue's life from a distance, suddenly feeling a hint of envy. The princess hopes to also encounter a good partner and live a happy life like theirs. She earnestly requests Ling Chang Jin not to disturb or harm Tang Qian Yue before she gives birth to her child.

Ling Chang Feng accepts Ling Chang Jin's invitation and meets him. He finds out the reason Ling Chang Jin wants to meet him is to find a way to save Chang Jin's sister. Ling Chang Jin brings Ling Chang Feng to the place where his sister lies. Ling Chang Feng realizes Ling Chang Jin only married Bao Zhu to get her Kirin Blood and starts to fight Ling Chang Jin.

After discovering that Lu Luo has become a Butterfly Slave because of her, Bao Zhu deliberately or inadvertently distances herself from Ling Chang Jin. Concerned about Bao Zhu's unimproved condition, Ling Chang Jin insists on taking her to see a doctor for treatment. While doing so, he notices a wound on Bao Zhu's hand and realizes that she had been extracting blood to give to Lu Luo.

Ling Chang Feng guards outside Tang Qian Yue's room for a night, but Tang Qian Yue still avoids him and won't meet him. Both people are angry, but they still care about each other. Tang Qian Yue covers Ling Chang Feng with a blanket and is found out. Both of them have a chat, and Ling Chang Feng seems to have given up on the idea of drawing the Butterfly Curse to the child.

Upon awakening from a nightmare, Tang Qian Yue finds the child but couldn't find Ling Chang Feng anywhere. Intuitively, she feels that something may have happened to him. When she presses for answers, Madam Yuan discloses to her that Ling Chang Feng uses curse inducement through blood relatives to induce the Butterfly Curse, ultimately drawing it upon himself, even though he knows it can be a life-threatening act.

Princess Bao Zhu falls unconscious in Ling Chang Jin's arms. He temporarily preserves her life using the Butterfly Curse. Carrying her, he seeks out Madam Yuan with the intention of riskily drawing the curse with blood to save her. After a month, Princess Bao Zhu regains consciousness, but Ling Chang Jin is nowhere in sight.

The commander watches from outside the house and sees how lively it is inside. He wants to use Ling Chang Jin as an excuse to leave but realizes Ling Chang Jin is also inside Ling Residence. Tang Qian Yue and Bao Zhu persuade him to stay and have New Year's Eve Dinner together.