Kim Woo Hyuk (Ma Ri's Partner) looks suspicious. He keeps on suggesting Yoo Ryung (YR), not to enter the tunnel, and that too avoiding the other detectives.  He might not be the killer - spasms.....but he definitely seems suspicious. Plus another character who might be linked to the ghost is the hospital caretaker.....she was s**t scared when she saw the video on phone (ep 5)

I don't know how, but I think the ghost is Yoo Ryung's sister, or someone she knew. Because the ghost made a move with his shoulder like her sister. And why especially they can't find her sister?! She may be became a partner.

I also think it will be someone who will surprise us.

i think the ghost have an assistant and shes yoo Ryung sister 

 Muna93:

yes he's very suspicious 

i think the caretaker is the ghost mom 

i think the ghost have an assistant and shes yoo Ryung sister 

 LakshP:

Kim Woo Hyuk (Ma Ri's Partner) looks suspicious. He keeps on suggesting Yoo Ryung (YR), not to enter the tunnel, and that too avoiding the other detectives.  He might not be the killer - spasms.....but he definitely seems suspicious. Plus another character who might be linked to the ghost is the hospital caretaker.....she was s**t scared when she saw the video on phone (ep 5)

But in the last Ep the ghost appears to kill the girl "who lost her bag" and the 4 characters were together in the station!!

Imagine how big the plot twist would be if the male lead is actually the subway ghost..

 Frost:

Imagine how big the plot twist would be if the male lead is actually the subway ghost..

Oh my God, I'm-

I don't know why I'm laughing omg :)))

 Paula:

Oh my God, I'm-

I don't know why I'm laughing omg :)))

I’m glad it made you laugh ◕‿◕

I know my theory sounds far-fetched, but it was worth a try lol.

 biased:

About 47:37 on episode 9, did you also notice the hair coming out of the hood?

Do you mean female? Great observation........