The sixth episode of Siren's Kiss begins with Woo-seok confronting Seol-ah about her parents' death. She admits to killing them, but then clarifies that she only said so because Woo-seok never believes her. Of course, Woo-seok doesn't know what to believe.
Seol-ah has a drink with Eun-hyuk and they talk about the past. A flashback shows that Eun-hyuk and Eun-hye's father was abusive. One day, Seol-ah stopped him from beating his children and took the other two to her own house. In the present, Seol-ah says Eun-hyuk gave her the courage to live, and Eun-hyuk says the same about Seol-ah.
At the police station, the detectives get permission to reopen the Kim Yun-ji case. At the auction house, Seol-ah gets ready for a new exhibition titled "Portrait of Women," featuring a painting of a siren. An interviewer asks her a few questions and brings up her fiancé's death to try and rattle her, but it doesn't work. We then see that the interviewer is working for Director Song.
Woo-seok comes to the auction house to deliver some papers. That's when Seol-ah receives an anonymous text with photos of her with Lee Su-ho and Woo-seok. The person blackmails Seol-ah, giving her an address to Felix Storage. Seol-ah goes to the storage office, followed by Woo-seok, and follows the texter's directions. In the end, she finds a picture waiting for her. It shows her and Seung-jae sitting on his boat, likely on the day he died.
Woo-seok, who is a few feet behind her, notices a box opening overhead and pushes Seol-ah out of harm's way. A ceramic pot falls down and shatters right next to her. Woo-seok had seen a person in a black cap right before this. Jun-beom arrives on the scene as well, explaining that he was thinking of hiring the storage facility for his own company. Despite the incident, the company does not reveal who the owner of the storage unit is.
On the drive home, Woo-seok and Seol-ah realize someone is following them. The car follows them all the way to the apartment complex where Seol-ah lives. She invites Woo-seok upstairs and then tells him the truth about her parents.
Her mother had given her some money and instructed her to go watch a movie. Instead, she had bought fried chicken for her family, only to find out that her parents had ingested pesticides and had spread gasoline all over the floor, making it appear like an accident. She had used a lighter to set the final touch, intending to die with them. But she had survived. Now, Woo-seok was hugging her and telling her to let it all out.
Meanwhile, an unidentified man was looking at photos of Seol-ah and Woo-seok, seemingly sent by the person who had been following them. At the police station, Director Song was helping the detectives identify everyone who had been at the party. Detective Pyo and Joo-young discovered that Seung-jae's boat had been sent for repairs the day before he died. They went to the repair shop where an employee told them there was an issue with one of the connecting wires of the engine. He also revealed that it wasn't Seung-jae but Eun-hyuk who had brought the boat to him.
Back at work, Seol-ah saw that Felix Storage was one of Royal Auction's storage companies. Her colleague said it was meant for Chairwoman Kim, but she didn't think anything was actually stored there. Seol-ah met the chairwoman who was currently packing jars of kimchi for her important clients.
The next day, Seol-ah told her junior colleagues that she would choose one of them to be the associate auctioneer. Woo-seok showed up and suggested they go out for lunch to discuss their suspicions about Jun-beom. She admitted that she felt like he already knew who she was. While they were eating, Royal Auction staff members, including Eun-hyuk, saw them.
Later, Woo-seok's contact looked into Jun-beom and showed him some pictures. One of them showed Jun-beom working with an organization called OnWorld, the same company that Lee Su-ho had been involved in when he went to Syria. Woo-seok visited the organization where he was told to contact an employee named Lee Kwang-jin who was currently out of the country. When he returned to his office, he was surprised to find Joo-young there, asking the insurance company to step back from the investigation. She accused him of not looking at the case clearly.
Joo-young shared the recordings she had obtained from Yun-ji's phone with her colleagues, while hiding the fact that Woo-seok had kept the evidence to himself. The detectives then called Eun-hyuk in, who said that Seol-ah had given him the key to the boat and asked him to get it repaired. At that moment, Seol-ah called Eun-hyuk but he cut the call.
Some time later, Lee Kwang-jin called Woo-seok and told him that Su-ho had died because of Seol-ah. He promised to explain everything when he arrived in the country. Woo-seok met him at the airport and gave him a ride. A person in a black cap followed them.
Kwang-jin remembered both men. He said Jun-beom had volunteered since he was in college and mentioned something about an incident in Syria with Su-ho, which is when the person in the black cap suddenly stopped their car in front of Woo-seok's. Woo-seok was forced to serve and the car overturned. As the other car drove away, a new one turned up and Seol-ah walked out, coolly looking at Woo-seok before he passed out.
