In the fifth episode of "Siren's Kiss," the narrative picks up after Seung-jae's memorial, where Seol-ah attempts suicide but is stopped by Woo-seok. He then shadows her, ensuring she reaches her destination safely.
Elsewhere, Director Song attempts to offer Jun-beom a deal for the Stiller, but Jun-beom reveals that he's going with Seol-ah instead, as she's agreed to advise him on a new fintech project named "Your Artwork." He offers her the role of CEO, but she declines.
Woo-seok tries to reach out to Eun-hyuk but is ignored. He then heads to Seol-ah's parents' house and enquires about the fire from the neighbors. Eun-hyuk eventually shows up and agrees to reveal the truth. He says that Seol-ah's father, Mr. Han, was a struggling artist who turned to loan sharks. Unable to repay them, the loan sharks branded little Seol-ah with an iron as punishment. Eun-hyuk watched the entire incident, and Seol-ah didn't utter a single scream. Shortly afterward, Mr. Han set the fire, hoping the entire family would perish together. Woo-seok visits Sook-ji next, who also insists that Seol-ah is innocent.
At the auction house, Seol-ah gives Chairwoman Kim good news about the Stiller. Later, Woo-seok goes to Yun-ji's secret apartment and listens to her recordings of Seol-ah. He sees Seol-ah on her balcony, and she seems to spot him too. When she goes inside, she has a small smile on her face.
The auction house then begins preparations for an exhibition by an artist named Kim Joon-young. Eun-hye deliberately breaks one of the glass pieces, although everyone thinks it's an accident. She compares this to how Seung-jae and Yun-ji are dead but there's no evidence to prove it. Seol-ah tells her to report her if necessary but to respect the art she works for.
They file an insurance claim, which means Woo-seok arrives on the scene and takes pictures. He insists on driving Seol-ah, who wants to go to the artist's house. At the office, we see that Eun-hye was working on Director Song's orders. It turns out that he told her to mess with Seol-ah in exchange for a permanent position at the company.
In the car, Seol-ah reveals to Woo-seok that she is aware of his spying from Yun-ji's secret apartment and warns him not to cross any boundaries. When they arrive at Kim Joon-young's studio, Seol-ah begs him to keep the exhibition open. She even assists in the remaking of the piece with Woo-seok's help, despite the flames from the furnace causing her to feel a sense of dread.
Afterwards, Woo-seok and Seol-ah discuss the misfortune that has befallen her, and she expresses that she finds her situation somewhat odd, suspecting that someone close to her is committing these murders. Woo-seok says he wants to believe her, but Detective Pyo continues to suspect Seol-ah.
Joo-young goes to Woo-seok's house but finds it empty. However, she does find Yun-ji's burner phone. When Woo-seok returns home, she confronts him about it, accusing him of being too sympathetic towards Seol-ah. She returns to the police station where her colleague notices a man filming the rooftop from the CCTV footage of Yun-ji's death. They decide to find the man and obtain the footage.
Kim Joon-young's exhibition is back on, with a new piece replacing the old one. Seol-ah tells Woo-seok that the artist isn't filing for insurance. He then proposes an idea - he will be her new man and together, they can find the culprit. Seol-ah agrees, saying she's curious to see the look on his face when he learns the truth.
The next day, Seol-ah and Woo-seok go to Park Jun-beom's place to oversee the transport of the Stiller painting. Jun-beom offers them a glass of wine and in the process, Woo-seok notices some bottles of Seung-jae's wine. Before they leave, Jun-beom tells Seol-ah that he has feelings for her.
As they're leaving, Woo-seok and Seol-ah discuss their suspicions about Jun-beom. They notice him watching and decide to test him by kissing! Back in the house, Jun-beom is clearly angry and throws his glass of wine on the floor. Meanwhile, Joo-young and her colleagues obtain footage from the person who was recording the rooftop. The footage shows someone on the rooftop looking down at Yun-ji's body.
At work, Woo-seok asks his boss to find records of a company named GW Life Insurance. Something in those papers shocks Woo-seok and he rushes to see Seol-ah. He shows her documents that prove Seol-ah's parents had insurance policies and the payout went to her. A flashback shows Seol-ah's mother, still alive, holding Mr Han's unconscious body as young Seol-ah drops a lighter onto the floor. At present, she tells Woo-seok that he's right - she started the fire.
