In the opening of Episode 11 of Siren’s Kiss, Seol-ah is seen hiding in Chairwoman Kim’s vault, where she is suddenly confronted by Woo-seok. The two manage to sneak out undetected as Chairwoman Kim enters her office. The next day, the auction commences, and during the final piece, a painting by the late artist Song Hwan-ju, Seol-ah shocks everyone by revealing the piece as a forgery. In front of an audience, she proves that Chairwoman Kim has been forging artworks and committing insurance fraud. Simultaneously, Woo-seok leads Detective Pyo to Chairwoman Kim’s secret vault, where Joo-young arrives and promptly arrests her.
While examining the pieces in the vault, Seol-ah and the others are surprised to discover the Stiller painting there as well. Woo-seok realizes that a forgery of the Stiller must be being made and rushes out. He tracks Hyun-su through his GPS tracker and follows him to the warehouse where the forgeries are produced. When Hyun-su is about to burn everything to the ground, Woo-seok stops him, leading to a confrontation. Hyun-su goads him by suggesting that his sister only wanted to marry to ease his burden, and that her death was Woo-seok’s fault. The others are forced to separate the two men.
Seol-ah allows Woo-seok to grieve and then takes him home, cooking a meal for him. This time, she tells him that she doesn’t want to push him away or run away. She wants to try being together and protecting each other.
At the police station, Detective Pyo and Joo-young interrogate Hyun-su. Later, they find text messages between Chairwoman Kim and Yun-ji that prove Yun-ji knew about the forgeries and the insurance fraud. A flashback shows Yun-ji blackmailing Chairwoman Kim and demanding the main podium.
Seol-ah returns to work, where many of the auction house’s clients have requested to cancel their consignments. Seol-ah takes responsibility for the situation and apologizes to her colleagues.
Elsewhere, Woo-seok discusses the situation with Joo-young. Despite everything, he doesn’t believe that Kim or Hyun-su are responsible for Seol-ah’s boyfriends’ deaths. Instead, they focus their attention on Eun-hyuk. At the same time, we see Seol-ah and Eun-hyuk talking. During their conversation, he makes cryptic remarks about how Seol-ah will get what she wants.
Surprisingly, Chairwoman Kim, with her fancy lawyers, is able to stay out of jail. She returns to the office where she and Seol-ah have an honest conversation. Seol-ah promises to take her down, but Kim seems confident that she's untouchable. After Seol-ah leaves, Kim calls someone and tells them to "take care" of Hyun-su, or else she will reveal their secret to Seol-ah. After the call, she brings out some ledgers from a secret compartment under one of the floor tiles. That night, while Kim is drinking and dancing inside her vault, someone wearing black gloves enters the room.
Meanwhile, Woo-seok goes through the CCTV cameras that make Eun-hyuk's alibi. The footage shows him entering and leaving his studio around the time of Jun-beom's death. The next morning, Seol-ah and Eun-hyuk both decide to quit. They go up to the chairwoman's office and end up finding her dead body inside the vault. The police arrive on the scene and find a suicide note on her laptop.
Seol-ah is shaken by the incident and tells Woo-seok that she thinks Kim was murdered as well. Suddenly, she drops the bottle of wine she was drinking - Seung-jae's bottle - and finds a note written on the inside of the label. The note says that Yun-ji visited him, but we don't hear the whole thing. Woo-seok then shows Seol-ah her parents' insurance papers, which have been signed by an agent named Kim Mi-suk. He also shows her photos from Jun-beom's house that show Yun-ji was in Cheongun on the day that Seung-jae was killed. This means she likely witnessed his death, which could be the reason she was killed.
The implications of these discoveries are kept a bit vague but the two of them jump into action after this scene. Woo-seok measures the distance between Eun-hyuk's house and Jun-beom's villa and realizes that it can be covered in 15 minutes. Woo-seok finds a key to Eun-hyuk's studio and searches the place, finding scuba equipment, a motorbike, and a back door leading outside. Simultaneously, Seol-ah goes to the office and goes through Eun-hyuk's things and finds Chairwoman Kim's bookkeeping ledger. Inside is proof that the chairwoman has paid many of Eun-hyuk and Eun-hye's expenses. At that moment, Eun-hyuk confronts Woo-seok, holding him at gunpoint.
