Another murder took place. So Yoon continues to clarify her sister's family line as she finds out about a certain disease. Pil Sung captures photos from So Yoon.

So Yoon is trying to convince Ga Young's mother about Ga Young's Fabry disease. Hyung Kil gives Woo Jae a task to find a walnut tree in order to catch the serial killer. Yoo Na is hospitalized by her mother.

The investigators are getting closer to the serial killer and set out a bait on the internet. So Yoon comes closer to finding out the biological father of Hye Jin.