It’s the summer of 2009 and Cheong Ah is a senior in high school who is the second of three daughters. Her parents run a small chicken restaurant while her older sister is a news anchor. Cheong Ah doesn’t have any hopes or dreams, and no one knows why, except for a friend she has only talked to via text messages. She skips school and gets on a train to go meet him where she runs into a handsome soldier.

The friend Cheong Ah plans to meet at the train station is Joon Kyum, a boy from a well-off family. The two teens plan to commit suicide together. They enjoy their last meal together and return to the small room they have rented, where Cheong Ah falls asleep. When she wakes up in the middle of the night, Joon Kyum is gone and only a letter remains. Cheong Ah calls her mom for help, who tells her to make everything look like an accident.

Cheong Ah must make a witness statement at the police station about Joon Kyum’s death, but she is still in shock. Her mom takes the lead, making things up as she goes. Judge Hong comes to the police station after identifying her son’s body. She is not only upset about her son’s death, but also suspicious of Cheong Ah’s story.

At home, Cheong Ah confesses why she wanted to end her life. Meanwhile, Seol Ah is searching for a fashion brand that will sponsor her wardrobe, but to no avail. However, Jin Woo overhears Seol Ah talking to the store employee and decides to sponsor her wardrobe personally. Finally, Cheong Ah must sneak out Joon Kyum’s letter from police evidence.

While Cheong Ah is on her way out of the police station with Joon Kyum’s letter, Judge Hong bursts in wearing her pajamas. Judge Hong tries to search Cheong Ah and when that doesn’t work, she requests an autopsy on Joon Kyum’s body. Meanwhile, Seol Ah pieces together the story and figures out what is going on. Later on, the police come to search Cheong Ah’s room.

Seol Ah sees her mom trying to hide Cheong Ah and Joon Kyum’s phones. She tells her mom that an inquiry at the phone service provider will reveal the call and text histories anyway. Meanwhile, Jin Woo brings in a reporter to spin the story of his cousin’s death in a favorable way to the family business. As the press begins to hound Judge Hong, she reconsiders the investigation.

The day of Jun Gyeom’s funeral arrives. Judge Hong calls Cheong Ah’s mom, Young Ae, and finds out that Cheong Ah went to school. However, Cheong Ah shows up at the funeral on her own. Chairwoman Hong, Jun Gyeom's aunt, takes her anger out on Cheong Ah. Meanwhile, Seol Ah goes on a blind date, but the man who shows up is not the person she expected to see.

Seol Ah’s blind date turns out to be better than she expected. However, when she comes home, she figures out that her date is related to Jun Gyeom. Seol Ah blames Cheong Ah for ruining her chances of marrying a rich man. Meanwhile, Judge Hong invites Cheong Ah to her house and asks to know the truth about Jun Gyeom’s death. Finally, a year goes by and Jun Hwi receives a strange letter.

Nine years after Jun Gyeom’s death, Cheong Ah studies to become a police officer. She takes the civil service exam for the seventh year running, but things don’t seem to go very well. Still, Cheong Ah tries hard, remembering Jun Gyeom’s last words to her. Meanwhile, Seol Ah lives a harrowing life as Vice Chairman Do Jin U’s wife, because she still doesn’t have a baby.

Cheong Ah’s friend Baek Rim asks her to fill in for him on a part-time job. She goes to the park, dressed as Mr. Lightning, to hand out flyers. Meanwhile, Jun Hwi, who now works at Inter Market’s Sports Marketing Department, is at the same park for a promotional event. Jun Hwi mistakes Cheong Ah as someone his team hired for the event. Finally, Seol Ah gets shocking news while visiting the hospital.

Jun Hwi visits Cheong Ah’s studio apartment in search of Rim, who he thinks is Mr. Lightning. Suddenly, Cheong Ah gets a call from the hospital. Rim is the victim of the car accident that Jin U caused, but he isn’t badly hurt. Jin U, on the other hand, is still unconscious after surgery. However, Seol Ah discovers that Jin U is having an affair. Seol Ah tries to keep Jin U’s affair a secret from Chairwoman Hong.

Jun Hwi visits Cheong Ah’s studio apartment in search of Rim, who he thinks is Mr. Lightning. Suddenly, Cheong Ah gets a call from the hospital. Rim is the victim of the car accident that Jin U caused, but he isn’t badly hurt. Jin U, on the other hand, is still unconscious after surgery. However, Seol Ah discovers that Jin U is having an affair. Seol Ah tries to keep Jin U’s affair a secret from Chairwoman Hong.

Cheong Ah shows up at Rim’s hospital room in the Mr. Lightning costume to prove her innocence to Jun Hwi. They go to the patrol division to let the police know what happened. After Cheong Ah’s name is finally cleared, Jun Hwi asks the Head of Patrol about the detective who handled Jun Gyeom’s death several years ago. Meanwhile, Seol Ah is in shock after hearing Jin U’s condition.

Cheong Ah and Jun Hwi return to the hospital together. Jun Hwi tells her to come by his office the next day to discuss the payment she owes for damaging the camera. Cheong Ah ends up telling Jun Hwi about Jin U’s car accident. Meanwhile, Chairwoman Hong is busy protecting Jin U’s assets from Seol Ah, who takes desperate measures to keep her place as Jin U’s wife.

Cheong Ah and Seol Ah run into each other in front of the ICU and they realize that they are both involved in the same car accident. Seol Ah tells Cheong Ah to keep their reunion a secret from their mom. Tae Rang sees Seol Ah waiting in front of the ICU and forces her to go eat with him. As they fall asleep in the hospital chapel, Jin U’s condition worsens.

Yeong Woong sulks over his wife’s supposed mistreatment of him and he sneaks out with Yeon Ah’s gold medal to replace with a fake. Jun Hwi submits a repayment contract regarding the camera that Cheong Ah damaged, but his boss is not happy about it. Jun Hwi calls Cheong Ah into the office to sign the contract. Meanwhile, Young Ae visits an OBGYN at the hospital where Jin U is being treated.

Cheong Ah runs into Chairwoman Hong in front of the elevators at Inter Market. Before Chairwoman Hong remembers who she is, Cheong Ah makes a run for it. Meanwhile, Young Ae discovers that she needs surgery. As she sits near the hospital, thinking about what the doctor told her, she sees Seol Ah for the first time in nine years. They have a brief, tearful reunion.

Seol Ah discovers Jin U’s generosity toward Hae Rang and her family and becomes even more enraged. However, Chairwoman Hong continues digging for evidence of Jin U’s affair to use as an excuse to get Seol Ah divorced from her son. Meanwhile, Young Ae discusses the accident with Cheong Ah and says that they must take Seol Ah’s side. Jun Hwi’s search for the girl from Jun Gyeom’s death continues.

Young Ae and Judge Hong meet in the lobby of the hospital. When Seol Ah shows up to meet her aunt-in-law, she’s surprised to see her mom there but pretends not to know her. Young Ae leaves the hospital in a hurry, but her legs give in from the shock of the encounter. Tae Rang sees her and helps her get home. Meanwhile, Cheong Ah confides in Jun Hwi regarding the accident.

Tae Rang brings home the food that Young Ae made for Seol Ah and delivers it the next day. Seol Ah thinks Tae Rang must have some other motive, clueless that the food is actually from her mom. Meanwhile, Chairwoman Hong continues to threaten Seol Ah with divorce, using the picture of Hae Rang and Jin U as proof of Jin U’s intentions. Finally, Judge Hong visits Cheong Ah at her studio apartment.

Cheong Ah and Jun Hwi meet at the accident site by chance. Cheong Ah tags along with Jun Hwi, whether he likes it or not. As they find evidence from the accident together, both Cheong Ah and Jun Hwi discover more about each other. Meanwhile, Seol Ah convinces Chairwoman Hong that they should be on the same side.

Tae Rang receives a phone call from Young Ae, asking to deliver another meal to Seol Ah. At the office, Chairwoman Hong bursts into Jun Hwi’s office and warns him to stay away from Cheong Ah. Meanwhile, Cheong Ah visits her mom, who gives her an envelope of money. While leaving her parents’ house, she runs into Mr. Cha, Chairwoman Hong’s secretary.

Seol Ah eats her mom’s food that Tae Rang delivers to her. When Chairwoman Hong sees Seol Ah eating, she suppresses her anger and begins her nice mother-in-law act, just as her lawyer suggested. Meanwhile, Yeong Woong comes home from the local welfare center empty-handed and tries to blame it on Young Ae, as usual. However, this time, Young Ae takes a stand.

Cheong Ah receives a phone call from Judge Hong, who asks Cheong Ah to join her for dinner. Cheong Ah hesitates, wondering whether she should meet Judge Hong or run and hide as Seol Ah told her to. Meanwhile, Jun Hwi gets called up to Chairwoman Hong’s office. He becomes worried that the chairwoman could have threatened Cheong Ah as well and goes to see her at the studio.

Hae Rang wakes up from her coma and Seol Ah finally finds out that Tae Rang and Hae Rang are siblings, not husband and wife. Seol Ah feels betrayed that she opened up to Tae Rang. Meanwhile, Inspector Mun decides to help Jun Hwi investigate the car accident. Finally, Rim and Jun Hwi meet outside Hae Rang’s hospital room.

Jun Hwi updates Rim about Inspector Mun’s involvement in the case and Rim tells Jun Hwi that Cheong Ah isn’t his girlfriend. Later, when they meet outside the hospital, Jun Hwi finds himself smiling when he sees Cheong Ah. Meanwhile, Seol Ah runs into Hae Rang waiting to see Jin U. The fight between the wife and mistress begins, as Chairwoman Hong intercepts a note from Tae Rang to Seol Ah.

Seol Ah comes home, and her family warmly welcomes. Seol Ah, Cheong Ah, and Yeon Ah have an honest talk for the first time in a long time. Meanwhile, Hwa Young thinks Seol Ah and Tae Rang are having an affair, and tells Hae Rang not to give up on Jin U and be his side.

While Seol Ah keeps her promise to Tae Rang that she won’t tell Hae Rang’s father about her affair, Chairwoman Hwa Young uses Hae Rang’s love for Jin U and asks her to make a false statement to the police. Cheong Ah tries to threaten Hwa Young with a recording to protect Rim.

Cheong Ah and Seol Ah threaten Chairwoman Hong with the voice recording. Cheong Ah deletes the recording, but Jun Hwi also pushes Chairwoman Hong to make a settlement with Rim. However, Chairwoman Hong presents Jun Hwi with a condition. Later, as Cheong Ah and Jun Hwi talk on the phone, Jun Hwi gets the feeling that Cheong Ah is the same person he met before.

Chairwoman Hong wants to throw Seol Ah out. But with the press starting to follow them for interviews regarding Jin U’s accident, she has to continue pretending to be a good mother-in-law. Meanwhile, Tae Rang tries to convince Hae Rang to do the right thing and leave Jin U, but she refuses to listen. Finally, Jun Hwi decides to ask Cheong Ah about the first guy she fell for.

Cheong Ah and Jun Hwi are glad to finally recognize each other from the train years ago, but Jun Hwi bids Cheong Ah farewell. However, when Jun Hwi goes to meet the high school tennis player he wants to scout, he realizes more about Cheong Ah and her family than he expected. Meanwhile, Young Ae is livid that Hae Rang is back in her daughter's life.

Tae Rang goes to see Chairwoman Hong and hands her a letter of resignation on behalf of his sister, but Hae Rang still wants to stay by Jin U’s side and eventually take Seol Ah’s place as his wife. Young Ae overhears Chairwoman Hong and Hae Rang’s conversation and lashes out at them both. Meanwhile, Cheong Ah’s exam results are finally out, but she is too nervous to check it herself.

A year passes by and Jin U finally wakes up from his coma. However, he and Seol Ah are already divorced. Seol Ah tries to live a new life, although she can’t help but visit Jin U every week. Meanwhile, Cheong Ah finishes her time at the police academy and gets her first assignment. When she reports for duty on her first day, she meets a friendly face.

Jin U is angry and confused about everything that happened during the past year. Meanwhile, Judge Hong invites Cheong Ah out to dinner to celebrate her first day of work. During their meal, Judge Hong gets a call from Jun Hwi saying that he is back. Finally, Yeon Ah decides that she wants to ask Jun Hwi whether the contract deal is still available.

Jin U is shocked to discover that he and Seol Ah are divorced and has a hard time accepting it. He finally realizes that Seol Ah knows about his relationship with Hae Rang. Meanwhile, Cheong Ah and Jun Hwi reunite and they both seem to have feelings for each other. However, Young Ae shows up to make things a bit awkward. Also, Jun Hwi remembers his mom asking him not to meet Cheong Ah.

In an attempt to regain Seol Ah’s favor, Jin U sends flowers and gifts to her house. However, Seol Ah refuses to let him sway her and sends everything back to him. Young Ae is furious that Jin U did such a thing without apologizing properly and goes to visit him in the hospital. Meanwhile, Jun Hwi signs a contract with Yeon Ah and uses the excuse to call Cheong Ah again.

Jin U follows Seol Ah as she goes to hang out with Tae Rang and confronts her. Jin U goes home angry and Hae Rang can’t do anything to make him feel better. Meanwhile, Cheong Ah begins training Jun Hwi to be less of a jerk. At home, Yeon Ah and Young Ae are concerned that Yeong Woong has housewife depression.

On Jin U’s first day back at work, he runs into Tae Rang in front of the Inter Market building. Jin U is surprised and bothered to hear that Tae Rang is Hae Rang’s brother. As the Sports Marketing Department gets an influx of support from Vice Chairman Do, Jun Hwi begins planning for bigger things. He goes to see Cheong Ah after work but finds an unexpected intruder already there.

As Cheong Ah and Jun Hwi officially start dating, Seol Ah is surprised to see Jin U waiting for her after work. Jin U wants to start over with Seol Ah, but Seol Ah is confused between Jin U and Tae Rang. After dropping Seol Ah off in front of her house, Jin U finds Seol Ah’s phone in his car. While trying to figure out how to return it discreetly, he runs into Yeong Woong.

Jin U tells Hae Rang that he wants to try to get back together with Seol Ah and Hae Rang is heartbroken. However, she does not plan to give up on Jin U just yet. Meanwhile, both Cheong Ah and Jun Hwi are excited for their first date. As they sit by the Han River, Jun Hwi seems excited to say something.

Tae Rang tells Seol Ah how he feels about her, but Seol Ah is unsure of what she should do. Meanwhile, Cheong Ah and Jun Hwi go to see a movie, but Jun Hwi’s odd behavior leaves Cheong Ah feeling frustrated. As Hae Rang warns Seol Ah to leave Jin U and her brother alone, Jin U decides to take another shot at winning Seol Ah’s heart and drives her old car to her house.

Jin U gets invited into the house by Yeong Woong and they both get drunk and fall asleep. Jin U wakes Seol Ah in the middle of the night and confesses that being in the same room as her makes his heart race. However, Seol Ah doesn’t feel the same way. Meanwhile, Jun Hwi must keep his relationship with Cheong Ah a secret from his mom.

Seol Ah finally confesses her feelings for Tae Rang and they enjoy each other’s company at Tae Rang’s restaurant. However, Jin U shows up out of nowhere and interrupts their intimate moment. Meanwhile, Jun Hwi takes Cheong Ah home and somehow ends up being beaten by Yeong Woong. Things get slightly awkward when Jun Hwi gets invited into the house.

Jun Hwi’s unusual behavior at home leads to Judge Hong figuring out that he has a girlfriend. Meanwhile, Hae Rang tells Chairwoman Hong that Seol Ah is using her brother for revenge after she is hurt once more by Jin U’s cold shoulder. Despite all the interference, Seol Ah and Tae Rang continue to enjoy their budding relationship by going to the market together.

Jun Hwi gets angry at Jin U, thinking that Jin U told Cheong Ah’s dad and sister that they are related. However, he realizes that nothing has been revealed yet. He goes along with the half-truth that Jin U makes up on the spot. Later, Cheong Ah gets upset that she knows so little about Jun Hwi. Meanwhile, Jin U sees Seol Ah and Tae Rang walking home and looking happy together.

Hae Rang tells Tae Rang that she has found out Seol Ah is the woman who Tae Rang has a crush on. She also says that she will marry Jin U, who is Seol Ah's ex-husband, at all costs. Meanwhile, Jun Hwi makes up his mind to break up with Cheong Ah after he has a talk with Seol Ah. He comes to see Cheong Ah.

Jun Hwi takes Seol Ah’s advice and tries to break up with Cheong Ah. However, his actions don’t convey the same message as what he is saying. Meanwhile, Jin U continues to pursue Seol Ah in every way he can think of. But no matter what Jin U does, Seol Ah keeps pushing him away. Lastly, Judge Hong says goodbye to Cheong Ah for good.

With the goal to be a reporter for a TV show, Seol Ah tries to shoot a video of her eating food at a restaurant by herself. But then, Tae Rang and his father suddenly come into the restaurant, and Seol Ah hurriedly leaves the place. Meanwhile, Cheong Ah and Jun Hwi have a date in an exhibition. They promise to go to Paris together in the future.

Jin U’s heartfelt apology still is not enough to change Seol Ah’s mind and only makes things worse between Jin U and Chairwoman Hong. Meanwhile, Seol Ah becomes worried that Cheong Ah’s feelings for Jun Hwi might get deeper. However, Jun Hwi seems to have no intention of breaking up and takes Cheong Ah to a comic book cafe for a sweet date.

Seol Ah gets to fill in for a morning show. She becomes so nervous before the show that she asks Tae Rang to come over to the broadcasting station. Jun Hwi hurriedly comes to Cheong Ah's house after hearing that Cheong Ah is hurt, but she's not home. Meanwhile, Cheong Ah has dinner and goes to a movie with Yu Ra.