"Good Doctor" Joo Sang Wook learns that Yoon Yoo Sun is Joo Won's biological mother.

September 16, an episode of the KBS drama "Good Doctor" featured Kim Do Han (Joo Sang Wook) feeling bad for Park Si On (Joo Won) after he faints from being shocked to see his father.

Kim Do Han says, "I think you should see your son another time. He is very unstable right now. We will let you see him when his condition stabilizes."

However Park Si On's father Park Choon Sung (Jung Ho Geun) yells out, "Who are you to get in the middle of father and son?" Right then, Pakr Si On's mother Oh Kyung Joo (Yoon Yoo Sun) arrives and says, "Listen to Professor Kim Do Han. Where do you think you are, behaving like that?"

Kim Do Han begins to become suspicious of Oh Kyung Joo for appearing out of nowhere to take control of the situation. Cha Yoon Seo (Moon Chae Won) later tells Kim Do Han that Oh Kyung Joo is Park Si On's biological mother.

Kim Do Han says, "Why didn't you say anything? You should have told me" and scolds Cha Yoon Seo. She replies, "She asked me to keep it a secret. I couldn't do anything because she asked me so desperately. The trauma he received from his father must be really serious if seeing him makes him faint like that."

Kim Do Han says, "We can't hide Park Si On's mother from him too."