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

Jae-won 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 Tae-ju to look into them. She feels sorry for suspecting her father, but regarding her husband, she becomes more certain about him having an affair.

Teo tells Yoon-jin that he saw her with Soon-young and that she should stop developing the relationship further. Jae-won 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 Jae-won was attacked and finds out who the perpetrator is.

Teo goes to confront the stalker who attacked Jae-won. 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 Jae-won looks for Chi-young, Soon-young’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.

Soon-young admits to dating Yoon-jin, and he asks for a divorce. He demands the custody of A-rin, but Jae-won refuses. Jae-won finds out that Yoon-jin has been picking A-rin up from her kindergarten from time to time. Yoon-jin’s portrait unveiling ceremony is held, and Jae-won prepares a special gift for her.

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

Soon-young recalls the day he got an email that revealed A-rin is not his biological daughter. After Jae-won realizes the reason behind Soon-young’s affair, she apologizes, but he doesn’t accept her apology. Jae-won decides to accept Soon-young’s terms and give up on A-rin.

Jae-won acts like a different person as if she had forgotten everything. Yoon-jin tries to make use of the situation, but Soon-young tells her to stay away from Jae-won. Soon-young takes Jae-won’s medicine pills to the doctor to find out what they are for. Meanwhile, Soon-young looks to find A-rin’s biological father with Teo's help, and Tae-ju meets Yoon-jin.

Jae-won’s father learns from Yoon-jin that Soon-young cheated on Jae-won. Outraged, he demands to know what Soon-young plans to do with Jae-won, and they both decide to keep Jae-won in the dark. Soon-young finds out who A-rin’s biological father is and what happened with Jae-won seven years ago.

Jae-won is accused of killing Soon-young and gets arrested. Circumstantial evidence points to Jae-won 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 called for a stockholders' meeting to dismiss Jae-won from the CEO position.

Jae-won and her father decide to send A-rin to America for her safety. Jae-won gets released from the mental institute and starts collecting evidence to prove who truly killed Soon-young. Meanwhile, Jae-won gets her hand on the data to prove that Kim Sang-bum manipulated the clinical test.

Jae-won is discharged, and she starts to put her plan into action. She visits Dereve and tells Yoon-jin that she will eventually get to her. Detective Oh Soo-jin looks into Soon-young’s case, and she notices that something is off. Jae-won goes to see Young-ik and tells him to choose the one that he wants to protect, his ministership or his daughter.

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

Yoon-jin finds Seung-kyu 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 Tae-ju, and Tae-ju goes off the grid. Meanwhile, Jae-won tries to find people who know about her mother’s past.

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