In the fourth episode of The Art of Sarah, the story unfolds with police officers canvassing the reservoir. They reconstruct a male skeleton in his 20s or 30s, raising concerns that it might be Ji-hwon. The cops rush to his place, only to find it in a mess, and Ji-hwon, alive but having a panic attack. He has scratches on his hand and declares that he has killed Sarah. Thus, his story begins.
A few years ago, while working as an escort, Ji-hwon met Kim Eun-jae, who, like Mok Ga-hui, used a fake name. She approached him, making him believe he was the one in power. Clearly, she was using all her tricks to make him feel special and important. She was married to Hong Seong-sin, an influential loan shark, and made it seem like he was abusive.
Every night, she had Ji-hwon take her out for midnight snacks, making it seem like she starved at home. As a token of appreciation for his companionship, she gifted him her husband's watch. But it wasn't enough as he had his own debts to pay. One day, he found needle marks on Eun-jae and believed her husband was forcefully drugging her. He decided to kill Seong-sin so that all of Seong-sin's assets would go to Eun-jae, and in turn, she could pay off Ji-hwon's debt.
But on the night of the attack, he accidentally stabbed Eun-jae who told him to run away. A few years later, she contacted him again, already donning her Sarah Kim persona. She lured him into seducing Chairman Choi with promises of marriage, a manager position at her Boudoir store, and even an apartment.
He soon started hating the arrangement and tried to stop it. However, Sarah let him in on her secret by allowing him to follow her to her tiny workshop where a bunch of laborers were making Boudoir bags with low-quality material. He saw it as a threat - that if he tried to take her down, he would go down too as an accomplice to a con artist.
Upset, he contacted Hong Seong-sin and told him all about Eun-jae's con on both of them. At present, Ji-hwon breaks down as he believes he pushed Seong-sin into killing Sarah. He comes off as a lovesick fool who would have joined her con if only she hadn't toyed with his feelings. Jae-hyeon feels sympathy for him, but Mu-gyeong sees through his act. Ji-hwon ensured that he looked good in his story so he wouldn't be charged as an accessory.
The scene is vividly portrayed through their interactions and emotions, making the story more engaging and relatable for the audience.
Next, the police officers visit Hong Seong-sin, who shares his tale with them. Seong-sin suffers from a failing kidney but has found no donor willing to help him. Frustrated and upset, he gets drunk and makes a scene. All the escorts run off except Du-a, aka Sarah Kim. She is unafraid of him and listens attentively to his rants. In exchange for 500 million won, she offers to be his donor. They enter into a fake marriage that must last at least a year for a spousal transplant. During this time, Seong-sin creates her Eun-jae persona, complete with an Oxford background. The needle marks are from the transplant check-ups. In that year, the two learn a lot from each other. He is actually soft and seems to give in to sob stories of his debtors while she is ruthless. And he teaches her how to lie, how to have a classy aura, and the idea of conmen turning into real businessmen. He tries to keep his distance but fails as she looks out for him of her own volition. After one luxurious party, she rants about being a fake. It is the night of Ji-hwon's plan and when he tries to kill Seong-sin, Sarah protects him. When she recovers from the stabbing, she asks about Seong-sin's kidneys. Seong-sin is so touched, he wills everything to her. On the day of the transplant, she runs off. Seong-sin's right-hand man has recognised her. He is the loan shark who harassed her two years ago. She knew who Seong-sin was and approached him to con him. His men catch her and are about to kill her when Seong-sin stops them as he claims he was under no delusions of who she was. She is moved and goes through with the kidney transplant. She then leaves with his 500 million won pine tree. He is amused and endeared by her. At present, Mu-gyeong realizes there is no transplant scar on Sarah Kim's dead body, which means she is still alive. He announces a nationwide search for her as a suspect, but we see that she is waiting for him at the precinct.
