In the review before the Jin Pil incident, Jin Pil was attracted by a message mentioning Shiyin's secret and went to the scene.Because of his curiosity, he was attacked from behind and injected with the same poison that was given to Se-yin.When the doctor reveals this to Sae-yin and the detectives, they are shocked and conclude that Jin Pil was not the one who poisoned him.The investigation is back to square one, unable to determine who the real murderer is.Dong-sik suggests that Se-yin seek police protection since she is at the center of the incident and could be the next target.Se-yin refuses the protection and tells Dong-sik to focus on catching the murderer.

The next day, Shiyin narrowed the scope of suspicion on the band members and focused on Luna, Yazhen, and Soojin because they fit Dongsik's description of the murderer, that is, a woman with type B blood.Dong-sik dispatched detectives to follow the three women, but no suspicious clues were found.So he turned his attention to poison, since only three laboratories had it.Dong-sik quickly gathered relevant information, while Jung-jae looked for clues from the documents in these research laboratories.During this period, Shiyin became suspicious of the people around him.Hye Jung saw her condition, asked her what happened, and learned about the poisoning.Hye-jung expresses her support for Se-eum, telling her that she won't run away because she wants to face the problem with her friends.Shiyin felt moved, but she didn't want the danger to threaten her father and friends.She goes to Jung Jae and asks him to protect the two if anything happens.

The next day, everyone is discussing a documentary about divorced couples and concludes that Ah Jin and Kim Pil did have an affair.Afterwards, Shiyin announced that the upcoming performance would be her last, as a fitting way to say goodbye to the band.Luna woke up to the sound of her sister and her fiancé quarreling. Eventually, they called off their engagement because her fiancé cheated on her, a fact that Luna already knew.Meanwhile, Dong-sik arrives at the lab where Jung-jae discovered something fishy, ​​and it’s quickly revealed that the person under suspicion is Luna’s brother-in-law, Kim Jin-young.Later, Luna tries to talk to Se-yin, but Jung-jae arrives and they go to Se-yin's office together.There, he asked her if she knew a man named Jin Jinyong or anyone at Xuanren Pharmaceutical.Shiyin doesn't recall anything, but as the two leave, her eyes fall on Hanfer's sign, which triggers a memory of her time at Luna's house.

Shiyin saw the Xuanren Pharmaceutical Factory logo on the calendar in her room, which meant she was related to someone there.She then remembers the scar she saw on Luna’s shoulder, which may have similarities to Dong-shik’s description of Bong-joo’s murderer.Connecting all these clues, Shiyin was shocked and she hurried to her office with Zhengzai.On the other hand, when Luna tried to run away from home, her brother-in-law asked him to steal Scotilamin for use.Elsewhere, Jung-jae and Se-yin finally find poison in a pot in her office.They have now identified the killer.Meanwhile, Tae-ho arrives and tells Jin-young to leave, and Luna, realizing something is wrong, invites Tae-ho into the house and hits him in the head with a pot when he's not looking.