Teenager Lee La-el witnesses the destruction of her family and murder of her father in a hostile takeover orchestrated by Han Pan-ro, a powerful former prime minister. La-el is adopted by Jang Moon-hee, a woman whose daughter was also murdered by Pan-ro. Moon-hee encourages La-el's need for revenge, and the pair prepare to punish Pan-ro and his right-hand man Kim Jeong-chul. Thirteen years later La-el, using the name Kim Sun-bin, has married Jang Ji-wook, who was also involved in Pan-ro's hostile takeover. Using this connection, La-el befriends Han So-ra, Pan-ro's daughter, and initiates an affair with Kang Yoon-gyeom, So-ra's husband. La-el is helped by Seo Eun-pyung, a congressman who was mentored by La-el's father, and who is in love with La-el. The plan was for La-el to access Yoon-gyeom's business files and file a lawsuit against Pan-ro, but when she learns that So-ra killed her mother, she escalates. La-el reveals the affair to So-ra and Ji-wook to sabotage both marriages, and encourages Yoon-gyeom to pursue business dealings that betray Pan-ro and his own father. Moon-hee realizes that La-el is falling in love with Yoon-gyeom. La-el and Moon-hee have a falling out, but agree to work on their revenge plans separately, with Moon-hee focused on filing the lawsuit. Yoon-gyeom files for a divorce; So-ra rejects it, but Pan-ro wants So-ra to accept and countersues Yoon-gyeom. So-ra discovers Moon-hee's connection to Pan-ro, and tortures her for information in the hopes of winning Yoon-gyeom back. When Moon-hee's lawsuit goes public, Pan-ro kills Moon-hee, and Yoon-gyeom realizes who La-el is and the extent of her manipulation. The police recover Moon-hee's body, and La-el finds a recorder in Moon-hee's clothes that has recorded Pan-ro, Jeong-chul and So-ra admitting their crimes. La-el shames Yoon-gyeom for his involvement with Pan-ro's crimes, though Yoon-gyeom protests that he didn't know the extent of them. La-el takes over Moon-hee's lawsuit and reclaims her true identity. She and Eun-pyung work together to make Pan-ro, So-ra and Jeong-chul turn on each other. Pan-ro tries to kill So-ra, who imprisons him in his mansion's basement. Yoon-gyeom holds a press conference admitting that violence was used in the hostile takeover, and endorses an investigation into the murders of Moon-hee and La-el's mother. Afterward, he disappears and leaves behind a will that assigns his company shares to La-el. Believing that Yoon-gyeom is going to commit suicide, La-el finds him and admits her true feelings for him. Jeong-chul tries to kill La-el, but is killed by Yoon-gyeom. So-ra kidnaps La-el, and in response Yoon-gyeom drives with So-ra off a cliff; Yoon-gyeom dies, but So-ra survives, goes crazy and is placed in a mental hospital. Pan-ro, abandoned, dies in his house's basement. La-el takes charge of Yoon-gyeom's company, turns it into a non-profit, and compensates all victims of the hostile takeover. She leaves for Buenos Aires, and some time later Eun-pyung travels there to find her, though La-el dreams of how her love with Yoon-gyeom might have gone if they met without pretense.
