Original: 펜트하우스
A woman puts everything on the line to achieve her goal of being able to move into a luxury penthouse in the Gangnam District. In the process, she gradually finds herself turning into a monster.
Yoon Hee's daughter dreams to be a classical singer. Despite her mom's disapproval, she's a feisty middle school student who pursues singing. One day, she visits the most famous soprano in Korea, Cheon Seo Jin. She wants to take her lessons and pleads her to accept her. Right when Seo Jin was astonished to hear her voice, Yoon Hee barges in, and the two meet unexpectedly.
All of Hera Club's middle schoolers aim to top the entrance audition to Cheong Ah Arts High School. Everyone busily takes their lessons and works hard and so does Ro Na, Yoon Hee's daughter. The big day arrives and everyone patiently waits for the results. A surprising name tops the list of successful applicants. It's an unheard girl named Min Seol A.
Seo Jin urges Seol A to sign a paper saying that she’ll give up her acceptance to Cheong Ah Arts High. Seol A doesn’t back down and firmly states how she’ll attend the school no matter what. On top of that, Seol A also mentions how she knows about Seo Jin and Dan Tae’s secret illicit love affair.
Due to Seol A’s death, Ro Na, the first on the waiting list of Cheong Ah Arts High automatically gets accepted. Unlike Ro Na’s jovial heart, Yoon Hee is confused and nonplussed at the news. She can’t remember what happened the day she went to Hera Palace.
Files of Hera Club kids harassing Seol A is spread online and the Hera Club parents find ways to circumvent the situation. They decide to shift the attention to Yoon Hee and make sure Ro Na is suspended from school. However, an unexpected man stands up for her at the emergency parent meeting.
Su Ryeon visits Congressman Cho to reveal the truth behind the countless orphans who were adopted but deported back. The two get in a fight as the discussion heats up and Mr. Yoon accidentally kills Congressman Cho by trying to protect Su Ryeon. Right then, the doorbell rings and Yoon Hee appears.
Yoon Hee decides to sell the Bosuk Village home she bought for her daughter’s sake. However, on the day Yoon Hee was supposed to sell the house, she sees the news of the city’s new redevelopment plan. Bosuk Village will be the main redeveloped area and she and Ro Na be rich now.
Su Ryeon intentionally allows Yoon Hee to see her husband having an affair with Seo Jin. Using Yoon Hee’s sympathy toward her, Su Ryeon moves on with her plans in bringing down Joo Dan Tae. The first step is by purchasing the building in the center of Myeongdong’s new shopping center site.
Because Yoon Hee won the auction bid for the Myeongdong house, Joo Dan Tae tries to win her over by offering a deal. However, Yoon Hee remains rigid and clearly states that she will not sell the building to Joo Dan Tae. The Hera Club men are infuriated and this time, Attorney Lee steps in to convince Yoon Hee in selling the Myeongdong house.
Yoon Hee moves into Hera Palace and the whole Hera Club is astonished. More surprisingly, it was Joo Dan Tae who wrote a recommendation letter, allowing her move-in. Ro Na and Yoon Hee enjoy their first day at Hera Palace while the others scheme to get her out.
Yoon Chul spots Seo Jin enjoying an intimate time with Joo Dan Tae. He's devastated inside and decides to get a divorce. Meanwhile, Cheong A’s audition to select the school’s ambassador is held and all of the Hera Club kids participate. As they audition, Seok Hoon hints a warm support to Ro Na, and Eun Byeol burns with jealousy.
Everyone practices hard to perform well at the Cheong A Ambassador Audition. Eun Byeol is on the verge to ruin herself as she grows agitated about competing against Ro Na and Seok Kyung. Seeing her daughter in panic, Seo Jin buys the audition script and hands it over to Eun Byeol to practice.
Yoon Hee finds out how badly Joo Dan Tae needs to meet Logan Lee to sell the Myeongdong plot of land. She and Su Ryeon plan to get back at Joo Dan Tae by arranging Logan and Dan Tae’s meeting at all costs. Will Logan buy Yoon Hee’s story and help her out?
At the lighting ceremony hosted to impress Logan Lee, Joo Dan Tae faces an unexpected surprise. Another hideous warning calling out Min Seol A’s death takes place and all Hera Club members are taken aback. Right then, Seo Jin steps up to confront Su Ryeon and exposes Su Ryeon’s relationship with Min Seol A.
Yoon Hee finds out how Ro Na has been misunderstanding her relationship with Yoon Chul. She decides to get back at Seo Jin for deliberately using her daughter to instigate Eun Byeol. Seo Jin and Yoon Hee meet, with another surprise guest Seo Jin would’ve never thought of in her dreams.
Seo Jin covers up her father’s death as an acute heart attack and acts as if she had nothing to do with it. After the funeral, she secures her position as the new director of the Cheong A Arts Foundation. Meanwhile, Logan Lee offers a co-investment plan to Joo Dan Tae.
Yoon Hee scans her memory to the night when Min Seol A died. She remembers that she was the one who pushed Seol A off the balcony of the 47th floor. Before she could even handle the truth, Su Ryeon confesses how she’s been using Yoon Hee to reveal the truth behind Seol A’s wrongful death.
Yoon Hee sees Dan Tae as a chance to elevate her daughter, Ro Na’s school life. Despite feeling some guilt about slowly growing distant from Su Ryeon, she partners with Dan Tae to also hide the fact that she’s the killer of Min Seol A. Meanwhile, Eun Byeol feels disgusted toward her mom after finding out about her affair with Mr. Joo.
On the day of Seo Jin's inauguration ceremony as the new director of Cheong A Foundation, a surprise text spread across the school. She's accused of forging Eun Byeol's admissions to Cheong A Arts High and captured. Dan Tae is also sued for embezzlement and finds out it was Logan Lee who reported him.
Seo Jin and Yoon Hee both beg Su Ryeon to stop now. They can’t bear seeing their daughters suffer from their wrongdoings, now being exposed. Su Ryeon tells them to turn themselves in and pay for what they did to Min Seol A.
Yoon Hee admits to killing Su Ryeon at the police station, but there’s actually a real culprit behind Su Ryeon’s murder. Joo Dan Tae planned to frame Yoon Hee and kill Su Ryeon together with Cheon Seo Jin. The two happily enjoy their freedom as Yoon Hee gets arrested.
