Killer theory

So Hey guys!!This drama is getting more and more interesting and hence I'm creating this discussion so that we all can share our theories about the plot here.

Here I'll be referring to the world in which seo Kyung dies as "World A" and the other as "World B" to avoid confusion.

So after 5 episodes in, I'm slowly getting an Idea about who would be the killer. And my choice is the Seo kyung's stepbrother in world B. Because all this started with the murder of their father which could have also been committed by him in world B. Also while he and do won got into a fight at care center, he said that "I killed them" which seems to point at his other version. 

Plus we see that in EP 5 in train, the killer limps which also matches with the stepbrother.

And as to why the murders never happened in world A I'm not yet sure but I think it has something to do with do won of World A and also because the stepbrother became mentally disabled.

I also found weird the limp in ep. 5 but don't think is the stepbrother, it's way to easy if it's him but the whole "I killed them" did put some doubs in my mind for a moment. After ep. 6 i think they planted the seed for the doctor so for now I had no proof that he is indeed the killer but I have no doubs either. 

My biggest question now is how in the name of hell did the stepmother became rich?

I thought stepmom got rich because of seokyung's dad insurance? In World B, it's likely that the stepbrother didn't get into an accident that would have otherwise cost them all of that insurance money. The psychiatrist and the Chief Section Oh are suspicious to me.
I wonder if the Chief Section Oh is the main villain though. She took Do Won in World A but not so in World B, and these two worlds diverged because in World A, Do Won decided to give up his umbrella to Seo Kyung and was stopped by one of the ahjummas so he couldn't stop his dad from getting hit by the car. I wonder if the Section Chief is involved in the hit and run and perhaps Seo Kyung's dad murder/

After seeing the end of EP 08 I'm quite disappointed ?... I was eagerly waiting for the world B do won to get into action but these damn writers killed him!!! He didn't even get enough screen time till now... Even though he was quite rude and unstable, I thought if both of them work together, they might catch the killer...

Okay... Now coming to the psychiatrist... I still don't think he is the killer... Because in episode 9 preview, the psychiatrist is shocked to see the do won alive which means he doesn't know about two worlds or that he has travelled to this world... But the killer knows this fact because he spoke with him in the phone in train... So I still hope that the killer is someone else... This psychiatrist might have killed the SK's father but I think someone else is behind the other murders... Let's wait and see what the train delivers in the remaining episodes!!!

But if the psychiatrist turns out to be the killer really, it would be more disappointing unless it is explained clearly...

The killer is the same, the only thing that change was that in world A the stepbrother and the psychiatrist had an accident and the first got badly hurt (as we saw) and the second one got killed (that's what I got from the photos that dead Seo Do Won finds in the other world). That's why the murders never happend in world A and Cheif Oh is not a horrible person in that version, at least that we know off.

And yes! I was so mad because weirdly they were the only couple that I liked and seeing her being like that, having to see the face of the man she loves but that isn't him, it kills me everytime.

 dragynfaerie:

I marathoned episodes 1-6.  From the beginning  I knew something was going on with her step brother  and the reveal in episode 10.  I didn't trust that character from the beginning especially in the 2nd world.  The character was just off to me.  I really felt bad for the forensics doc not being  able to openly mourn the man that she loved.  The question is who killed the fathers in world 1.  I still think it's the same characters.