It seems to be in the hospital because there is a smiling mask in a guy seen by Tae Han. Does it must be a student girl because I suspect the doctor. At first, just like Hwa Sun I keep suspecting that girl, Han Dong Rim. But she seems nice.

I think it’s the assistant nurse that’s currently in the hospital, not the one who was kidnapped by the murderer. She has red lipstick like the serial killer wears. 

 NotKirito:

I think it’s the assistant nurse that’s currently in the hospital, not the one who was kidnapped by the murderer. She has red lipstick like the serial killer wears. 

I missed seeing her scene.

also if it was the schoolgirl, Hwa sun would have recognized her.  because she was a foster parent to that young female serial killer who killed her husband. 

 NotKirito:

I think it’s the assistant nurse that’s currently in the hospital, not the one who was kidnapped by the murderer. She has red lipstick like the serial killer wears. 

I am also not sure which nurse was that one.   the only one I know is the one kidnapped by the prisoner. 

I think it's Yoon Saetbyul...

The doctor seems suspicious too.....

 NotKirito:

I think it’s the assistant nurse that’s currently in the hospital, not the one who was kidnapped by the murderer. She has red lipstick like the serial killer wears. 

I just watched episode 7. Well damn I guess I was wrong lol