Sun Jeong shares the same birthday as her three kids, Bit Chae Woon, Hae Deun, and Ra Hoon, so they plan to have a big party in the evening. Sun Jeong's sister Man Jeong visits the family to celebrate her birthday. Somehow, Chae Woon isn't too happy to see Man Jeong. Jae Hee goes to see Jung Won and Seo A be with them on a special day. Meanwhile, Chae Woon gets a call she's been waiting for.

After Bit Chae Woon meets a woman who could be her biological mother, she feels sorry for Sun Jeong. Sun Jeong thinks the woman who had approached her is strange, which leaves her feeling unsettled. Meanwhile, Bit Chae Woon's siblings discover she is looking for her biological mother, which starts a huge argument among them.

Out of anger and frustration, Chae Woon heads to the CEO of LX Fashion's house. At the gate, she faints, and Jung Won takes her in. Jung Won promises Chae Woon that she'll look into the case. Later, Jung Won calls Chae Woon into the office to explain the evaluation process. Even after hearing the explanation, Chae Woon still wants to prove her innocence, so Jung Won offers her an internship instead of giving her the prize.

Chae Woon loses her patience and lets all her frustration out on Sun Jeong. Hae Deun, Ra Hoon, and Man Jeong stick up for Sun Jeong, but they each get a taste of the painful stories she had been keeping inside. Man Jeong, who gets the worst of it, goes out drinking solo and returns on Hwak Se's back. The next day, Chae Woon realizes she's lost her cell phone.

Jae Hee is welcomed by everyone at Samgwang Villa. Chae Woon starts working at LX Fashion and has a hard time getting up to speed. A new tenant moves into the basement floor of Samgwang Villa. When Jae Hee recognizes him, he's very suspicious of his intentions. Sun Jeong helps out with the party at her boss' house and runs into Jung Won. Jung Won recognizes Sun Jeong.

After reuniting with Jung Won, Sun Jeong, without knowing, feels immensely guilty about her happiness to see her. Jae Hee is thrown into a storm of confusion when he learns about Chae Woon's past, and Min Jae shouts a startling remark at Jung Hoo, who had been secretly tailing her. Meanwhile, Chae Woon confronts Seo A when she sees she was deliberately excluded from the interns' presentation.

Jung Won receives a mysterious call regarding her lost daughter. She's shaken over it. Hae Deun causes trouble again, and this time, she used Man Jeong's credit card without permission. Out of frustration, Man Jeong leaves Samgwang Villa. Chae Woon looks for Park So Mi, the girl who framed her for bullying Seo A back in middle school. However, So Mi pretends not to know about it. Meanwhile, Min Jae sends her divorce lawyer to Jung Hoo.

Sun Jeong gets Chae Woon to tell her what's going on, and Chae Woon explains it's about Seo A. Jae Hee finds out where So Mi, Seo A's middle school friend, works and tells Chae Woon. Later, Jae Hee tries to talk some sense into his dad, but instead, he ends up renouncing his inheritance. Meanwhile, Chae Woon visits So Mi and Hae Deun auditions for Slight Entertainment.

Jung Hoo gets on his knees and begs Min Jae to come back home, but Min Jae doesn't falter in her determination to get a divorce. Jae Hee overhears Hae Deun and Ra Hoon talking and finds out that Hae Deun didn't pass the audition. Jung Won and Sun Jeong meet up for dinner and catch up with each other. Jung Won is happy to reminisce about the good old days with Sun Jeong, but Sun Jeong isn't so comfortable with her. Min Jae and Jung Hoo end up getting divorced, leaving Jae Hee heartbroken.

Chae Woon tries to console Jae Hee about his parents' divorce, while Jung Hoo adjusts to living alone. Later, Jung Won asks Sun Jeong to prepare a dinner party for Seo A and her team at her house. Meanwhile, Man Jeong gets caught sneaking back into Samgwang Villa to grab her things, but Sun Jeong won't let her leave. Later, Jung Won visits Pil Hong at the correctional facility and asks him about the suspicious person lurking around her.

Jung Hoo wakes up in the emergency center but doesn't remember who he is. Sun Jeong sees he's having trouble, so she decides to let him stay at Samgwang Villa until he recovers fully. Jung Hoo begs Sun Jeong and Hwak Se not to tell anyone else that he's staying at their house, so they decide to keep it a secret from the other residents. Meanwhile, Seo A sees Chae Woon's baby photo and realizes that she was the baby in the photo that Jung Won had.

Ra Hoon tells Jae Hee about the suspicious offer Hae Deun got from a new agency. When Hae Deun is about to sign the fake contract, Jae Hee and Na Ro show up to save her. However, Hae Deun feels more embarrassed than grateful. Sun Jeong gets invited to the launching event party of LX Fashion. There, she sees Jung Won being sweet to Chae Woon.

Sun Jeong tells Jung Won that Chae Woon is her daughter, and upon hearing the news, Jung Won is all the more glad to have her as her employee. Jae Hee finds out that Jung Hoo is suffering from amnesia and decides not to tell anyone his identity for the moment. Seo A invites Jae Hee to the team dinner and introduces him as her boyfriend. Worried that Chae Woon might get the wrong idea, Jae Hee tells everyone that he and Seo A are just friends.

Jae Hee takes Jung Hoo to get a checkup at the hospital. He finds out that he's perfectly fine. He questions for a moment that Jung Hoo could be lying but soon figures out that he's not. Jung Won gets invited to Samgwang Villa, where she meets everyone. Seeing how Chae Woon admires Jung Won so much, Sun Jeong decides to tell Chae Woon the truth. Meanwhile, Chae Woon rejects Jae Hee, saying she wants to be on good terms with Jung Won.

Sun Jeong tells Chae Woon that Jung Won is her birth mother. Shocked and confused, Chae Woon yells at Sun Jeong for not telling her sooner and insists on seeing Jung Won right away. They go to Jung Won's house, but they can't bring themselves to go inside. The next day, Jung Won asks Chae Woon to accompany her to the columbarium where she put the urn of her daughter, which she thought she had lost. Chae Woon is shocked by the fact that Jung Won thinks she doesn't exist in this world.

Chae Woon can't bring herself to go back home as she suddenly feels isolated and alone. She decides to have a sleepover at her friend's house, making Sun Jeong even more worried. Min Jae visits Jae Hee's neighborhood and sees Jung Hoo walking by. Chae Woon calls in sick because she's not ready to face Jung Won at work. Worried that things will get worse, Sun Jeong decides to meet Jung Won herself and tell her the truth.

Sun Jeong tells Jung Won about how Seo Yeon came to be with her, but Jung Won has a hard time believing her. However, they end up in a scuffle that Chae Woon sees. Jung Won faints and gets taken to the hospital. Later, Sun Jeong tries to tell Chae Woon why she didn't tell her that Jun Won is her biological mother, but Chae Woon reminds her that she doesn't want to know and that she is her mom.

Sun Jeong and Jung Won decide to tell Chae Woon about the DNA test results. Although Jung Won expresses her wishes to be Chae Woon's mom, Chae Woon refuses. After Sun Jeong and Chae Woon return home, the residents of Samgwang Villa get together for dinner. Meanwhile, Jae Hee helps Jung Hoo attend an emergency board meeting at the office.

Jung Won comes to Samgwang Villa to see Chae Woon, but she can't bring herself to take Chae Woon with her. Sun Jeong, along with everyone else, is shaken by the fact that Chae Woon could leave them anytime soon, but Chae Woon decides to stay with Sun Jeong, no matter what happens. However, Sun Jeong decides it's better for Chae Woon to live with Jung Won when he realizes how Pil Hong can mess up Chae Woon's life.

By chance, Chae Woon picks up a call from Jung Won's mom and hears things she shouldn't have heard. She decides to live with Jung Won to understand what really happened when she was young. Min Jae barges into Samgwang Villa in the middle of the night and finds Jung Hoo in Jae Hee's room. Jae Hee tells her that Jung Hoo has amnesia, and Min Jae is devastated. Meanwhile, Jae Hee finally finds out who Na Ro really is.

Chae Woon leaves Samgwang Villa and arrives at Jung Won's house. There, she meets Chun Seok, her grandmother, who had tried to blame everything on Sun Jeong. Seo A explodes into a jealous rage over Chae Woon's arrival. Meanwhile, Na Ro lashes out when Jae Hee suspects his motives, and Jung Hoo continues to get headaches when he starts to remember more from his past.

Min Jae comes to take Jung Hoo home, but he can't believe that Min Jae is his wife. Meanwhile, Hwak Se goes to sing at an event where Man Jeong is present. She sticks up for Hwak Se in front of all her friends, and they have a heart-to-heart conversation. Later, Jung Hoo wakes up in the hospital to find Jae Hee and Min Jae at his bedside.

Jung Hoo wakes up in the hospital with his memory restored. He heads home with Min Jae and Jae Hee. Meanwhile, Jung Won asks Chae Woon to open up to her more, but the mood in the house gets awkward when Seo A's jealousy continues to grow. Later on, Na Ro goes to see Seo A, and the pair come up with a scheme to get Chae Woon in trouble.

Chun Seok tells Sun Jeong to leave for Chae Woon's sake, but Sun Jeong stands her ground. Jung Hoo feels lonely now that he's back home, and Jae Hee suggests that they don't let the residents of Samgwang know about his memory coming back. Meanwhile, Chae Woon takes on a big project at work, but someone gets her into trouble on purpose.

Chae Woon tries to find out who's behind the conspiracy to sabotage her, but that only creates bigger gaps between Chae Woon and Jung Won. When Jae Hee finds out about what happened to Chae Woon, he suspects Na Ro and warns him to stay away from Chae Woon. Meanwhile, Sun Jeong finally makes up her mind to take action for Chae Woon.