Due to the release of a new product, Seo Jaewon stays in the office by herself till late at night when her longtime stalker barges into the office, trying to attack her. Later, Jaewon finds out the stalker’s identity. Nam Taejoo, an insurance investigator, tells Jaewon that they’re suspecting Jaewon’s stepfather of her mother’s death. Meanwhile, Jaewon sees a suspicious message on her husband’s phone, only to find out later that he is cheating on her.

Jaewon wakes up at the hospital after the incident. Because her company is launching a new product soon and she doesn’t know who the attacker is, she decides to let it go for now. But since she can’t trust the people around her, she asks Taejoo to look into them. She feels sorry for suspecting her father, but regarding her husband, she becomes more certain about him having an affair.

Yoon Teo tells Kwon Yoonjin that he saw her with Heo Soonyoung, and that she should stop developing the relationship further. Jaewon finds out that her dad used the insurance proceeds to pay off her late mother’s gambling debt. Teo restores the recording of the night Jaewon was attacked and finds out who the perpetrator is.

Teo goes to confront the stalker who attacked Jaewon. But before Teo meets him, the stalker gets in an accident and becomes unconscious. Teo tries to find out who is behind the stalker, and Jaewon looks for Heo Chiyoung, Soonyoung’s twin brother. She thinks that his existence is the only explanation for what has been happening to her lately. However, the investigation leads to another mystery.

Soonyoung admits to dating Yoonjin, and he asks for a divorce. He demands the custody of Heo Arin, but Jaewon refuses. Jaewon finds out that Yoonjin has been picking Arin up from her kindergarten from time to time. Yoonjin’s portrait unveiling ceremony is held, and Jaewon prepares a special gift for her.

Jaewon decides to get a divorce, but she can’t give up the custody. However, Soonyoung is most likely to take the custody because he spent more time with Arin. To turn the table around, Jaewon frames Soonyoung for leaking confidential documents. While doing so, Jaewon notices that she also has a critical weakness. Meanwhile, Teo continues to investigate and find out who tried to kill Baek Seunggyu.

Soonyoung recalls the day he got an email that revealed Arin is not his biological daughter. After Jaewon realizes the reason behind Soonyoung’s affair, she apologizes, but he doesn’t accept her apology. Jaewon decides to accept Soonyoung’s terms and give up on Arin.

Jaewon acts like a different person as if she had forgotten everything. Yoonjin tries to make use of the situation, but Soonyoung tells her to stay away from Jaewon. Soonyoung takes Jaewon’s medicine pills to the doctor to find out what they are for. Meanwhile, Soonyoung looks to find Arin’s biological father with Teo's help, and Taejoo meets Yoonjin.

Jaewon’s father learns from Yoonjin that Soonyoung cheated on Jaewon. Outraged, he demands to know what Soonyoung plans to do with Jaewon, and they both decide to keep Jaewon in the dark. Soonyoung finds out who Arin’s biological father is and what happened with Jaewon seven years ago.

Jaewon is accused of killing Soonyoung and gets arrested. Circumstantial evidence points to Jaewon as the killer, but the police can’t find the crucial evidence to indict her. She gets freed for lack of evidence and goes to her father’s place to rest and avoid reporters. Meanwhile, Chairman Kwon Youngik called for a stockholders' meeting to dismiss Jaewon from the CEO position.

Jaewon and her father decide to send Arin to America for her safety. Jaewon gets released from the mental institute and starts collecting evidence to prove who truly killed Soonyoung. Meanwhile, Jaewon gets her hand on the data to prove that Kim Sangbeom manipulated the clinical test.

Jaewon is discharged, and she starts to put her plan into action. She visits Dereve and tells Yoonjin that she will eventually get to her. Detective Oh Soojin looks into Soonyoung’s case, and she notices that something is off. Jaewon goes to see Chairman Kwon and tells him to choose the one that he wants to protect, his ministership or his daughter.

Chairman Kwon tries to kill Jaewon with a pesticide, just like he did with Soonyoung. Teo comes to the rescue, and Jaewon barely manages to survive. At the parliamentary inspection of the Ministry of Culture and Tourism, Jaewon reveals that Chairman Kwon is responsible for her kidnapping and Soonyoung’s murder. Chairman Kwon gets arrested, but Jaewon doesn’t feel like it’s over.

Yoonjin finds Seunggyu who has been hiding from her. She fails to persuade him to side with her, and she kills him without hesitation. She frames his murder to Taejoo, and Taejoo goes off the grid. Meanwhile, Jaewon tries to find people who know about her mother’s past.

Yoonjin decides to get rid of Taejoo so he won’t be able to reveal the last card he has on her. However, her plan fails, and Taejoo appears in court to take the witness stand. Jaewon gets her hand on the video and tells Yoonjin to come clean. When Yoonjin refuses, Jaewon decides to use Taejoo to get her.

Yoonjin takes Arin, and everyone looks for them. Jaewon finds Arin safe at home, and she asks her father to live with them together. A year later, Jaewon works as a freelance designer, and Teo becomes the CEO of Dereve. While doing so, Jaewon confronts her past and the resentment that has been following her to move on.