Moon Hee (Kang Soo-yeon), a seventeen-year-old high school student, lives with her mother Ha Soo-jung (Kim Hee-jin) in a single-room basement apartment. Like her friends, she attends an after-school academy after her classes are over, but unlike them, she must rush off to a barbequed pork restaurant as soon as she is finished with her studies. She works late into the night carrying dishes, cutting meat and cleaning tables. After 11 p.m., she even has to scrub off pork grease stains from the grills. She finally drags herself home tired after midnight. When Moon Hee was a child, Soo-jung was an ambitious and high-spirited young woman who tried her hand at running a flower store and a bakery and had passionate love affairs with many men. But now, all that has left is depression brought on by her extreme poverty, and Moon Hee is the only one she can lean on.

Yoo-jin (Jo Yeon-woo) follows Moon Hee (Kang Soo-yeon) on her business trip. He prepares to propose to Moon Hee with a surprise event in a hotel suite, but his plans are dashed by the sudden appearance of Moon Hyun (Lee Jae-eun). Moon Hee states that she wouldn't have accepted the marriage proposal even without Moon Hyun's sudden intrusion. It's the day of Ha-neul's birthday, and Jang Han-na (Kim Hae-sook) and her family celebrate it together. Meanwhile, Moon Hee broods over on her son whom she was forced to give up, who must be celebrating his birthday somewhere.

Young-chul, who had been spending his days in a mountain cottage after being released from jail, is reunited with his children San, Deul, and Ha-neul, and his wife, Jang Han-na. Han-na is deeply tortured as she watches Young-chul embrace his son, Ha-neul because she has to hide the secret of Ha-neul's birth from her husband. She comforts herself under her breath by telling herself that even though she may have to pay for her sins later on, she can be happy right now. Then, Ha-neul is sent to purchase champagne at a ski resort convenience store where he runs into Moon Hee.

Upon returning home, Moon Hee rushes into the bathroom, ignoring Sook-hee's words. Sook-hee tries pounding on the bathroom door, but Moon Hee does not answer her. Enraged, Sook-hee slaps Moon Hee as she comes out of the bathroom. Moon Hee kneels in front of her angry stepmother, telling her that she wants to be a good daughter, imploring her to trust her.

Yoo-jin visits the I-Mall Department Store in order to have lunch with Moon Hee, but she is too busy. Then, Yoo-jin runs into Moon Ho and asks him to help him marry Moon Hee, but Moon Ho replies that he should forget about her. Meanwhile, Sook-hee works hard on finding a suitable husband for Moon Hee...

In order to prevent strife within the family and the family business, Moon Ho tells Moon Hee that she should go to Japan. Being very fond of him, Moon Hee is hurt by Moon Ho's recommendation. Moon Hee refuses Yoo-jin's proposal by saying "Marriage is merely a luxury to me." Moon Hee sends Ha-neul a text message asking him to go out for ice cream with her...

Director Yoo Hyun-jong notifies Chairman Moon that he will look for another business partner for his hospital project. Also, Director Yoo tells Chairman Moon that he wants Moon Hyun and Yoo Jin's marriage to be called off. Chairman Moon doesn't understand Director Yoo's abrupt change of heart. Director Yoo tells Chairman Moon that both of Moon's daughters, Moon Hyun and Moon Hee, are in love with his son, Yoo Jin, so the marriage has to be called off. Having learned of Moon Hee's relationship with Yoo Jin for the first time, Chairman Moon is enraged and says that he will not forgive anyone who ruins his business. Meanwhile, Yoo Jin drags Moon Hee out of her arranged date and she goes to the grave of her mother, Soo-jung. She introduces Yoo Jin to her deceased mother saying that he is the man that she loves deeply. However, she whispers to Soo-jung that she may not be able to see Yoo Jin anymore.

Returning home with Yoo Jin's ring on her finger, Moon Hee tells her father, Chairman Moon, that she will marry Yoo Jin. Chairman Moon tells Moon Hee that she is tearing the family apart by loving Yoo Jin and asks her to spend a few years abroad. When Bang Sook-hee tells her to get out of the house, Moon Hee replies that she will not be intimidated out of her own home and that she would not have come here in the first place had she planned to leave so easily. Meanwhile, Ha-neul, who is waiting for Moon Hee, calls her since she doesn't show up. Moon Hee, who fell asleep in her car, wakes up upon receiving his phone call.

Moon Hyun asks her sister-in-law, Choi Sang-mi how she can break Moon Hee and Yoo Jin up. Sang-mi reminds Moon Hyun that Yoo Jin has a kind of obsessive-compulsive disorder and cannot stand people who lie. She instructs Moon Hyun to find out what happened during the 2 years that Moon Hee spent away from their home. Moon Hee, who has spent a fun day together with Ha-neul, embraces him in her lap and tells Kim Young-chul that a child she knows is also 11 years old and has the same birthday as Ha-neul. Meanwhile, Jang Han-na is worried sick since Young-chul and Ha-neul have gone to meet Moon Hee, but they haven't called her. When Young-chul returns home, Han-na is so upset that goes out and heads to Cheonggyecheon Stream. Walking at Cheonggyecheon Stream, she sees a woman who resembles Ha-neul's birthmother walking towards her and her heart begins to pound.

Having received a flyer for Haneul Martial Arts Academy, Moon Hyun is reminded of the photograph of Young-chul and Ha-neul she saw saved in Moon Hee's cell phone. Moon Hyun puts the flyer back into the newspaper and place it in Moon Hee's room. When she sees Moon Hee react to the flyer, Moon Hyun accuses Moon Hee of hiding something and pushes Moon Hee to reveal the truth about her past. Moon Hee, Managing Director Kim and Manger Oh discuss what to do about the expensive fake cosmetics they have been selling. Manager Oh says that when this hits the press by noon of the next day, the media and consumer groups will have a field day with this and that Moon Ho will receive the brunt of the blame. Moon Hee asks that she be made the chair of the solution committee of the I-Mall for the problem. Meanwhile, Yoo Jin calls Sook-hee and tells her that he is planning to make his engagement with Moon Hee official.

In order to throw Moon Hee out, Sook-hee gets rid of Moon Hee's things such as her refrigerator and her dresser. Yoo Jin, who comes to Moon Hee's place in order to propose to her officially, sees what is going on. Hearing that Yoo Jin is planning to visit Moon Hee's place, his mother Jin Soo-ja, waits there for Moon Hee, and asks her the truth about her past when she arrives. Moon Hee hesitates to give an answer to the sudden question. Meanwhile, Han-na, who had been momentarily shocked when she met Ha-neul's birthmother, calms herself and arrives back home. Han-na tells her mother-in-law, Song Ok-hee, that she wants to be beaten and asks her to beat her like she used to. Song Ok-hee begins to beat Han-na on the legs with a stick...

Upon seeing Young-chul being unable to fall asleep after having chilbotang decoction, Mu-seol goes to wake up Han-na and send her to look after Young-chul. But Han-na cannot get up because she is too drunk. Meanwhile, Moon Hee, who has been thrown out of her home, is spending the night at a hotel. Yoo Jin visits her with a single rose and they end up spending the night together.

The media finds out about the fake cosmetics of I-Mall on the day of Moon Ho's inauguration as I-Mall's CEO. When it is found out that Moon Ho has received stocks from the company that sold the fake cosmetics, the inauguration is called off and he is made to organize a solution committee. Also, Chairman Moon decides to hand down the hospital to Moon Hee when he hears that Director Yoo has decided to let Moon Hee and Yoo Jin marry. Meanwhile, Moon Hee becomes the head of the solution committee and Yoo Jin is reminded of the fact that Moon Hee told him she began to live with Chairman Moon in order to get revenge.

Sang-mi's aunt who has been trying to find dirt on Moon Hee presents Sang-mi with a picture of Sutbul, the man who Moon Hee once lived with. Enraged, Sang-mi says that she will never forgive Moon Hee for ruining her dreams and Moon Ho's life. Sang-mi confronts Moon Hee and tells her that she will make Moon Hee regret that she ever met her and that she will take everything Moon Hee has away from her. Meanwhile, Mu-seol receives baby's articles and a pager number that Ha-neul's birthmother left from her nurse friend who works at the hospital in Tongyeong where Ha-neul was born.

As I-Mall's majority stock holder, Sang-mi tells Chairman Moon to fire Moon Hee. When Chairman Moon refuses based on all the things that Moon Hee has done for the company, Sang-mi informs him that Moon Hee's real reason behind coming to him is to take revenge on both him and his wife. Chairman Moon promises to get rid of Moon Hee without hesitation if he discovers that she has come to him with malicious intent. Meanwhile, Mu-seol and Han-na agonize over what to do with the pager number of Ha-neul's birthmother, Ha Moon-hee. Mu-seol pages the number and waits a call from Moon Hee, saying that they should find out the truth.

Sang-mi goes to the barbequed rib restaurant that Sutbul runs and tries to draw information from him by telling him that he looks familiar. When Sutbul replies that he once ran a gas station in Jinju, Sang-mi asks him if he wasn't with a pretty looking woman at that time. She catches Sutbul's momentary change in expression and keeps asking him further questions such as whether that woman was his girlfriend or wife. Meanwhile, Moon Hee goes to the hospital in Tongyeong and begs Nurse Ju-yeong to be allowed to see her long lost son Ha-neul just once. But Ju-yeong replies that it's already been 10 years since Moon Hee parted with her son and she should forget about him.

Moon Hee meets Mu-seol and asks him about her long lost son. But Mu-seol says that Moon Hee's son was sent abroad and he doesn't know anything about him. Moon Hee sits alone in a marketplace and drowns her sorrows in a couple of drinks. Then, she staggers into Young-chul's martial arts academy. There, she runs into Young-chul and Ha-neul who are about to go home. She takes Ha-neul into her arms and begins to cry. Moon Hee confesses to Young-chul about her long lost son whom she bore at the age of 19. Meanwhile, Sang-mi's uncle who has been investigating Moon Hee's past goes to the hospital in Tongyeong. While asking about the records of Ha Soo-jung, Moon Hee's deceased mother, he shows a photograph of Moon Hee to Nurse Ju-yeong.

Having overheard the phone conversation between Moon Hee (Kang Su-yeon) and Sutbul Kim Seong-su, Yoo Jin (Jo Yeon-woo) asks her who she was talking to. But she gives him a false reply, telling him that it is a person from the solution committee. Yoo Jin thinks that it's someone she doesn't want to talk about, but later on hears from Manager Oh that there is no such person on the solution committee. Sang-mi (Lee Seung-yeon) goes to Moon Hee at her work and causes a scene, slapping her with all her might. She tells Moon Hee that the slap is for making her husband into a bum and that the slap is only the beginning of her revenge. Meanwhile, Chairman Moon (Lee Jeong-gil) tells Bang Sook-hee (Kim Yeong-ran) and Sang-mi to set up Moon Hee's room in the house again, so she can move back in. He warns them that the only way he'll give Moon Ho (Jeong Woong-in) another chance is if the two let Moon Hee back into the house without causing any problems.

Moon Hee (Kang Su-yeon) meets Sutbul Kim Seong-su and screams at him, accusing him of being her mother's murderer. To make up for his past sins, Kim Seong-su gives her a bankbook for an account with 20,000 dollars in it. And in between the pages of the account, there is a letter telling Moon Hee that the time he spent living with her was the happiest time in his life. Outraged, Moon Hee tears up the letter and throws it into a trash bin. Meanwhile, Sang-mi's aunt who has been keeping an eye on Kim Seong-su calls Sang-mi and urgently requests her to come to the barbequed rib restaurant. There, Sang-mi acquires the pieces of the letter that Moon Hee ripped up and threw into the trash bin.

Sang-mi, Bang Sook-hee and Jin Soo-ja, Yoo Jin's mother, await Moon Hee and Yoo Jin at Sutbul Kim Seong-su's restaurant in Yangsuri. Soo-ja says to Sook-hee that there isn't much time until the wedding and that they should prepare the traditionally exchanged jewelry between the bride and groom soon. Sook-hee replies that Soo-ja should try not to be too hasty because she won't be able to get back half the money she paid for the jewelry when she tries to sell it again. Unaware of the situation, Soo-ja asks Sook-hee what she is talking about. But Sang-mi doesn't let Sook-hee answer. Meanwhile, Yoo Jin is shocked when Moon Hee tells him that she once lived with another man. Yoo Jin cuts her short telling her that he doesn't want hear it. And he sullenly drives towards Yangsuri with Moon Hee in his car. As soon as Moon Hee and Yoo Jin arrive at the restaurant, Sang-mi orders 5 servings of ribs and requests that the owner of the restaurant serve them their food.

Jang Han-na visits the I-Mall in order to return the fake cosmetics that she purchased there when she runs into Moon Hee. Moon Hee cries and asks Han-na about the child that she gave birth to. She asks whether her child takes after her in any way, but Han-na replies that he doesn't look like her at all. And when Moon Hee beseeches Han-na to let her see her child just once, if only from a distance, Han-na refuses, saying that Moon Hee should know better than that. Meanwhile, after thinking deep and hard, Yoo Jin picks up the phone and calls Moon Hee. Moon Hee answers the phone, but Yoo Jin remains silent on the other end of the line.

After drinking with Moon Hyeon, completely inebriated Yoo Jin walks into his house drenched in rain. Then suddenly, he gets on his knees in front of his father, Director Yoo, and his mother Jin Soo-ja, and begs them to forgive him. When his mother asks him what he wants to be forgiven for, he replies that he cannot part with Moon Hee even if it breaks his mother's heart and even if she disowns him. Shocked and frightened, Jin Soo-ja asks Yoo Jin if Moon Hee is hiding something about her past to which Yoo Jin answers in the affirmative. After some thought, Jin Soo-ja asks her son if the owner of the barbequed rib restaurant was Moon Hee's old boyfriend and asks him about the extent of Moon Hee's relationship with him.

When Han-na tells Mu-seol that she will arrange a meeting between Moon Hee and Ha-neul, Mu-seol feels a sense of foreboding and tries to dissuade her. But she does not succeed in changing Han-na's mind. Mu-seol then meets with Moon Hee and informs her of Han-na's decision to let Moon Hee meet with Ha-neul. She requests that Moon Hee tell Han-na that she doesn't need to see Ha-neul anymore. Although Moon Hee is taken aback upon hearing that Han-na has told her family that she gave birth to Ha-neul, nevertheless, she turns down Mu-seol's request, saying that she'd like to see Ha-neul from afar just once. Meanwhile Bang Sook-hee meets with Jin Soo-ja and asks her if she knows about Moon Hee's promiscuous past.

Moon Hee awaits her son at the location in front of the museum as she agreed with Han-na. Moon Hee is standing there lost in thought and, Ha-neul appears and calls her excitedly, surprising her. Ha-neul asks her if she wants to go get some soda to which she replies that she has a very important meeting and requests that Ha-neul go away. Tense and tired of waiting for Han-na, Moon Hee calls Mu-seol's cell phone. Moon Hee is shocked when she suddenly spots Han-na and Ha-neul in the distance. Realizing that she had known that Ha-neul is her son all along makes her shed endless tears thinking of the amazing coincidences that brought her and her son together and all the times they shared with each other. With a million thoughts rushing through her head, Moon Hee collapses onto the pavement, unconscious.

Sang-mi, who has come to the hospital to pick up Moon Hee, who had fainted, becomes suspicious when she spots Moon Hui talking to Nurse Ju-yeong. Meanwhile, putting the picture of Moon Hee into the cabinet in Yoo Jin's room, Soo Ja discovers the empty ring box which Moon Hee gave back to Yoo Jin. It's the grand opening of Young-chul's martial arts academy. Ha-neul calls Moon Hee with an invitation but she declines abruptly. Meanwhile, Moon Hyeon visits the grand opening of Young-chul's academy and asks him if he won't teach a self-defense class at the department store culture center.

Before taking a bath, Moon Hee opens the necklace pendant with the picture of her and Ha-neul together, momentarily gazes at it, and leaves it on the edge of the sink. Moon Hyeon suddenly barges into the bathroom saying that the toilet in her bathroom is broken. Moon Hee leaves the bathroom, leaving the pendant on the sink... Meanwhile, Jin Soo-ja who had been agonizing over the situation with Moon Hee and her son, calls Moon Hee and asks to meet. As soon as she enters the room, she screams at Moon Hee and asks her how she could do such a thing. She begins hitting Moon Hee all over as Moon Hee kneels in front of her in shame. Soo- ja bursts into tears and screams at Moon Hee. She tells Moon Hee that Yoo Jin can't live without her and that she doesn't ever want to see her again.

Seeing Ha-neul and Moon Hee together, Jang Han-na goes ballistic and begins screaming at Moon Hee. Then, Ha-neul asks Han-na if she knows Moon Hee, but Han-na replies that she doesn't and suppresses her rage. Now, Ha-neul formally introduces Moon Hee to his mom, Han-na. Meanwhile, Jin Soo-ja visits Bang Sook-hee at her home and tells her that Moon Ho has the reason that he is infertile.

Moon Hyeon shows Sang-mi Moon Hee's pendant with the picture of Ha-neul in it. The two exchange a conversation in which they say that there must be a reason that Moon Hee is close to Ha-neul's father. Sang-mi laughs saying that Moon Hyeon has hit the jackpot. Also, Sang-mi meets Moon Hee and compares her to the picture of Ha-neul. Sang- mi tells Moon Hee that she and Ha-neul look alike and that people could mistake them for mother and son.

Sang-mi hears from Bang Sook-hee that Moon Ho is infertile. On that day, Mu-seol approaches Moon Ho about having an affair with her. She tells him that she would feel too pathetic if he turned her down right away and requests that he think about it and call her with an answer later on. Moon Hyeon meets Young-chul and asks him if all three of his children are really his. She says that Ha-neul doesn't look like him at all and asks him if Ha-neul is adopted. Young-chul answers Moon Hyeon that all of his three children are his, but becomes suspicious because of Moon Hyeon's questions. Meanwhile, the hospital calls Sang-mi with the results from Ha-neul's DNA test.

Moon Hee confesses the reason that she was forced to put Ha-neul up for adoption to Sang-mi. But Sang-mi cynically accuses Moon Hee of being a hypocrite and when Moon Hee begs Sang-mi not to reveal the secret for fear of the havoc it would reek on Ha-neul's life, Sang-mi coldly replies that she will only do that if Moon Hee leaves I-Mall and calls off the wedding. Meanwhile, fearful that the secret behind Ha-neul's birth will be revealed, Han-na goes to an overseas study agency in order to send Ha-neul abroad to study and asks them to find a place for him to study as soon as possible.

Moon Hee and Yoo Jin spend a cozy evening at Yoo Jin's house, cooking together and dining together. Jin Soo-ja then gives Moon Hee a gold ring, a family heirloom which she inherited from her grandmother. But burdened by the recent events, Moon Hee declines the ring saying that she does not know if she deserves such a precious ring. But Director Yoo tells Moon Hee that because Yoo Jin loves her and because she will be his and his wife's only daughter-in-law, she deserves the ring. This heartwarming statement brings tears to Moon Hee's eyes. Meanwhile, Young-chul finds out that Ha-neul is not his real son and calls Moon Hee and asks to see her, saying that it's in regard to Ha-neul.