Do Eun, Yi Chul's mistress, exposes herself and their baby on her social media on purpose, and the whole world finds out about their affair. Ji Chang and Hye Won are on Soo Hyang's side for the divorce trial and try their best to comfort her. Meanwhile, Ji Chang prepares a gift for Hye Won before their wedding.

Ji Chang promises Hye Won to find her long-lost sister, Hye Ji, no matter what. Hye Won discovers Yi Chul has been embezzling company funds under a shell company for two years. Meanwhile, Do Eun is curious about Ji Chang's fiancé and wants to meet her.

Do Eun plans to meet her soon-to-be daughter-in-law and rear-ends Hye Won's car to get things started. She then buys an art piece from her gallery. To learn more about the painting, Do Eun offers to have dinner together. At the dinner, Eun notices the pendant necklace around Hye Won's neck that she once shared with her biological sister.

Do Eun realizes Hye Won is her biological sister, whom she separated from when they were young. Meanwhile, Hye Won is confused about why Do Eun left in a rush from their dinner. Later, Hye Won learns Do Eun is Yi Chul's mistress and becomes furious.

Kyung Ja appears unexpectedly and ruins Hye Won and Ji Chang's wedding while Do Eun watches from the sidelines. However, Do Eun sees Min Tae, her father, and she begins to remember the past. Meanwhile, Myung Ae can't believe the disgrace Hye Won brought to the family and scolds Ji Chang.

After ruining Hye Won's wedding, Do Eun plots another scheme to bring her down with Kyung Ja. Hye Won and Ji Chang return home without going on a honeymoon, and Hye Won even sees Do Eun in her dream. While Myung Ae gives Hye Won a hard time at home, Do Eun sends a text message to Hye Won.

Do Eun suggests to Hye Won that they meet and talk in person. Do Eun sends her a photo of her necklace to convince her that she is her younger sister, Hye Ji. Hye Won waits for Hye Ji at the mineral spring, but a man shows up instead of Hye Ji.

Do Eun becomes furious after the protest in front of the Boram Childcare Facility. Do Eun suspects Hye Won is the one responsible for the protest and calls her to meet. Meanwhile, breaking news of Yi Chul's large donation to the Boram Childcare Facility by using a shell company airs, along with Do Eun's position in the facility.

Hye Won is disappointed after learning that the phone number that said it was Hye Ji is from a burner phone. Meanwhile, Myung Ae visits the temple and discovers from the monk that Yi Chul will have another child of great importance, and Do Eun takes off to get some air.

After learning that Soo Hyang will be holding a talk concert, Do Eun appears at the event and asks a question during the Q and A time. Hye Won is astounded by Do Eun's appearance and tries to remedy the situation. Meanwhile, Soo Hyang realizes the woman is Do Eun.

Since Young Ju and Jang Gun cannot reach Do Eun anymore, they change their target to Hye Won. To bring Hye Won down, Do Eun runs a background check on Judan Foundation for Arts and finds out about Dan Ung, who signed with the gallery. Not long after Do Eun's confrontation, another shocking news about Soo Hyang breaks out.

Dan Ung frames Soo Hyang for sexual assault and disappears. No matter how hard Hye Won tries to reach him, he is nowhere to be found. Meanwhile, Ji Chang suspects Do Eun, so he wants to meet her in person to reveal the truth.

Ji Chang encounters Do Eun directly, only to find that she doesn't match the image of recklessness he had anticipated. Upon Ji Chang's return, Hye Won expresses her disappointment in his apparent favoring of Do Eun. Meanwhile, Soo Hyang intends to pay Attorney Song a visit.

Hye Won tries to find Dan Ung, who has gone out of contact, to no avail. She returns home but gets further frustrated when Ji Chang thinks the opposite about Do Eun. To make matters worse, Do Eun tells Yi Chul about what Hye Won did to her when they coincidentally met and gets Hye Won in trouble.

Hye Won and Ji Chang are traumatized by Yi Chul and Soo Hyang's divorce, and Ji Chang starts to resent Do Eun even more. However, Myung Ae invites Do Eun over to their place. Meanwhile, Jang Gun and Young Ju visit Hyangdan Agency to find Hye Won and run into San Deul.

Hye Won and Do Eun meet again when Do Eun visits her in-laws at home. Do Eun shares surprising news, and Hye Won feels uncomfortable around her. The memory of their childhood unexpectedly overtakes Do Eun, but she tries to pull herself together for revenge. Meanwhile, Hye Won and Ji Chang grow apart after Do Eun joins the family.

Hye Won is stunned to learn that Dan Ung has departed the country, particularly shocked when she discovers his destination is Mauritius. Do Eun's fake pregnancy approaches revelation as she's guided, somewhat reluctantly, to the OB-GYN. Meanwhile, Sung Yoon establishes a law office conveniently close to San Deul’s tteokbokki spot.

Do Eun uses her wits to overcome the crisis of her fake pregnancy getting exposed. Meanwhile, Hye Won searches for evidence that Do Eun was behind the incident involving Soo Hyang. She resorts to apologizing to Do Eun to get the answers she needs.

Hye Won finally meets Lim Dan Ung face-to-face. After acquiring the evidence that would clear Soo Hyang's name, she hands it to Soo Hyang. However, Soo Hyang tells Hye Won that she will take care of it and calls Do Eun to meet.

Now that Soo Hyang has the recorder from Dan Ung, she decides to talk to Do Eun in person. She asks Hye Won to keep it a secret from Ji Chang as she wants to handle it on her own. When Soo Hyang calls Do Eun to confront her with the evidence, Do Eun flips out and asks for forgiveness.

Before Soo Hyang exposes the truth, she passes away due to a heart attack. Do Eun brazenly attends the funeral in a mourning dress, which makes Hye Won and Ji Chang infuriated. Hye Won quickly leaves the funeral after she gets a call from Dan Ung, and Do Eun tries to stop her. Meanwhile, Sung Yoon attends the funeral after hearing the news and runs into Hye Won.

Hye Won heads directly to meet Lim Dan Ung, but upon arrival, she is met with a disturbing scene. Despite the confusion, Hye Won gathers her resolve to uncover the truth behind the suspicious deaths. Meanwhile, Myung Ae instructs Hye Won and Ji Chang not to conceive a child until Do Eun delivers her baby, but it may be a bit too late.

After bumping into Hye Won at the pharmacy, Sung Yoon notices that Hye Won is pregnant. However, she doesn't recognize him and goes on her way. Meanwhile, Do Eun moves in with the family and begins to get under Hye Won's skin. Their new life under the same roof begins, but Hye Won has no intentions of giving in to her.

Young Ju and Min Tae run into each other and ask about their daughters, Hye Won and Hye Ji. Min Tae lies to her by saying Hye Won is studying abroad to protect Hye Won from her. Meanwhile, Do Eun lies to Ji Chang about what happened between Soo Hyang and her at the hotel, and now, she wants to set up a fake miscarriage and put the blame on Hye Won.

Do Eun gets anxious after she finds out Hye Won is pregnant. Moreover, Myung Ae makes it clear to Do Eun that she will only let her join the family after she gives birth to Yi Chul's child. Therefore, instead of faking the pregnancy, Do Eun changes her plan to actually get pregnant this time. Meanwhile, Sung Yoon wants to help Hye Won with Dan Ung's case.

Do Eun loses her mind as her plan falls through. Now that she cannot get pregnant, her hatred for Hye Won grows even bigger and threatens her for having a baby. Hye Won and Ji Chang quarrel over Dan Ung's case, and Myung Ae orders Hye Won to retrieve Dan Ung's art pieces back from their family.

Ji Chang learns about Hye Won's pregnancy indirectly and reacts coldly. Hye Won tells him she didn't have the courage to tell him the news, but it doesn't work. Meanwhile, Do Eun communicates with a baby broker so that she can continue to hide her fake pregnancy.

Hye Won is upset at how things between Ji Chang have become regarding her pregnancy. She talks to Min Sook about it to feel better. Meanwhile, Do Eun sees San Deul talking with Hye Won and realizes he is her brother and the person who had been looking for her. She makes up her mind to get close to him.

Hye Won and Ji Chang are at odds over matters at both work and home. Ji Chang wants Hye Won to let go of Dan Ung's case, but Hye Won is not willing to give up on it. Meanwhile, now that Do Eun realizes San Deul is in love with her, she tries to make use of him to get revenge on Hye Won.

Do Eun spikes the porridge San Deul got for Hye Won. Hye Won gets suspicious of the way Do Eun acts, but Ji Chang thinks she is being overly sensitive. Meanwhile, Do Eun witnesses Hye Won and Sung Yoon together.

Min Tae comes to see Hye Won at her place and runs into Do Eun. When Min Tae realizes that Do Eun is his long-lost daughter, Hye Ji, Do Eun threatens him to stay quiet. Meanwhile, Hye Won asks Do Eun about what happened between Min Tae and her earlier in the day, and Do Eun shoves her as hard as she can so that she falls down.

San Deul falls for Do Eun's trap and makes reservations with Hye Won for fish porridge. She also suggests taking Sung Yoon along for the trip. Meanwhile, Do Eun brings up Sung Yoon's name with Yi Chul regarding the attorney position at the company.

Hye Won and the party of people headed for lunch fall into Do Eun's trap, and they all get taken to the emergency. Meanwhile, Min Tae meets Young Ju with money to keep her away from Hye Won, but Young Ju makes a scene. Just then, Min Tae's phone shows Hye Won calling that Young Ju sees.

The whole family finds out Hye Won is pregnant, and Do Eun throws a fit at Kyung Ja as both Hye Won and her baby survived the car accident. However, Ji Chang and Hye Won's misunderstanding grows deeper after the porridge incident as Do Eun planned. Meanwhile, Min Tae worries about Hye Ji and waits for her to reach him.

Hye Won figures out Do Eun is not pregnant, but she decides to stay quiet and keep an eye on her. Ji Chang straightforwardly asks Sung Yoon if he has feelings for Hye Won. Meanwhile, Hye Won runs into Young Ju at the bank.

Min Tae comes by Do Eun's place to ask for forgiveness, and Hye Won advises San Deul to stop seeing Angela. Sung Yoon and Hye Won look for Do Eun's pawn to expose her for instigating murder. Meanwhile, Ji Chang's childhood friend, Ji Eun, joins him for his next project.

Sung Yoon keeps his promise to Hye Won and tails Do Eun to find evidence. Luckily, he follows her to the OB-GYN clinic Do Eun attends and discovers her fake pregnancy. After hearing this from Sung Yoon, Hye Won takes the evidence and confronts Do Eun to make a crushing deal.

As Hye Won confronts Do Eun with her infertility diagnosis, Do Eun confesses to Hye Won that she is her sister, Hye Ji. Now that the inevitable has come, Do Eun worries anxiously about all her heinous deeds and visits Sung Yoon. Meanwhile, Ji Chang's friend Ji Eun appears.

Hye Won and Sung Yoon pressure Do Eun to find Kyung Ja, and Do Eun pays Young Ju to help her with her schemes. After Do Eun discovers that Ji Eun and Ji Chang are close friends even at work, she decides to use Ji Eun to tear Hye Won and Ji Chang apart.

After the elevator accident, Hye Won heads to her father's place to rest, and Ji Chang follows her to beg for forgiveness. Ji Chang finds out someone else sent the text message to Hye Won through Ji Eun's phone. Furthermore, Sung Yoon suspects Do Eun as the culprit behind the elevator accident.

The house turns upside down as Do Eun's fake pregnancy and infertility are revealed. The whole family realizes they have been completely fooled by Do Eun, so they kick her out of their house. Do Eun ends up barging into Min Tae's place, and Hye Won lets Ji Chang know that Do Eun is her long-lost sister, Hye Ji.

Do Eun runs away, but Hye Won notices her missing and chases up to her. Shortly after, Min Tae comes to save Do Eun but gets into a hit-and-run accident, losing his life. Draped in sorrow, Hye Won swears at Do Eun she won't stop until she takes her down. Meanwhile, Do Eun blackmails Ji Chang for money.

Hye Won tells Ji Chang that she can't live with him, and Ji Chang tries to figure out how he can protect both the company and Hye Won. Meanwhile, Do Eun trembles in fear when she learns that Hye Won might get her hands on the evidence of her murder instigation.

Do Eun finds out Hye Won has the recorder and she is about to head to the police station to report Do Eun. Do Eun steals a delivery truck and follows Hye Won to stop her. Therefore, Hye Won ends up losing consciousness in the middle of the road.

Hye Won gets disappointed in Ji Chang again as she realizes he stopped the investigation for the car accident. However, he feigns ignorance and even gets mad at her for suspecting him. Meanwhile, Yi Chul promises Do Eun to run away together, and Myung Ae tells Hye Won to leave Ji Chang and her son.

Hye Won witnesses Ji Chang having an affair with Ji Eun. Hye Won wants a divorce, but Ji Chang is not letting her leave him easily. Do Eun heads to YJ resort that's under renovation to meet Yi Chul. Meanwhile, Sung Yoon runs into Ji Chang at a memorial park and follows him to find out what he is up to.

Hye Won rushes out to look for Ji Chang, but she witnesses Hye Ji get into a disastrous hit-and-run accident. Hye Ji goes in for surgery, but she falls into a coma. Meanwhile, Ji Chang goes missing, and Hye Won worries he might have to do something with Hye Ji's accident.

After the autopsy, Hye Won learns that Ji Chang died from a hit-and-run accident. With that information, Hye Won and Sung Yoon search for the culprit behind Ji Chang's murder. Meanwhile, fake news about Hye Won and Sung Yoon's affair surfaces and causes mayhem for Hye Won in Ji Chang's household.

Do Eun miraculously wakes up after the car accident, but loses her memory as Do Eun. Furthermore, the doctor mentions that she also shows signs of delusion, but Hye Won is not sure if she is delusional or just lying. Five years later, Jun Mo flies back to Korea and looks forward to meeting Hye Won after a long time.

Do Eun gets a part-time job as a cleaner and remembers something about Yi Chul. Even when Yi Chul is locked up in prison, he orders his assistant to keep an eye on Do Eun and waits for her to regain her memory. Meanwhile, Hye Won and Sung Yoon have a meeting with Jun Mo at Hye Won's office.

To get Jun Mo to invest in YJ Group, Sung Yoon decides to quit as Jun Mo requested. However, Hye Won tries to come up with a strategy to keep Sung Yoon by her side. Meanwhile, Ji Eun wants to bring Hye Won down through Jun Mo, and Do Eun visits Yi Chul to find out about her past.

Jun Mo offers Sung Yoon a chance to work together, but Sung Yoon feels his proposal is a trap. Hye Ji worries she might end up in jail and attempts to feel out Hye Won if she has the voice recording of her as evidence. Meanwhile, Yi Chul threatens Hye Won with the clause in her deal regarding her son and pushes her to get him out of prison.

Hye Ji starts to remember things in fragments, and Hye Won looks for a way to force Hye Ji into hospitalization. Meanwhile, Sung Yoon gets his hands on a dashcam video that shows Cha Ji Eun at the scene of Ji Chang's death. Later, they track her down to get her to confess.

Yi Chul is released from prison, and Do Eun makes a deal with him by giving him information about Jun Mo. The wife of Assemblyman Cha Sang Beom, Ji Eun's mother, visits Hye Won to warn her about her revenge. She firmly believes that Hye Won is responsible for Ji Eun's death. Yi Chul also joins her in kicking Hye Won out of YJ Group.

Do Eun tries to find the voice recorder and get rid of it before Hye Won does as she realizes that Hye Won is planning to lock her up in a closed ward. Do Eun gets closer to Jun Mo as Yi Chul tells her to and stalks him to find his weakness and report it back to Yi Chul.

Young Ju tails Hye Won as Do Eun told her to, and Hye Won finds the voice recorder that Ji Chang hid at the memorial hall. However, someone hits her in the head from behind and steals the recorder. Meanwhile, Sung Yoon finally confesses his feelings to Hye Won.