OKAY so I just finished watching the episodes and I have a lot of speculations!
I think that the main culprit is the actual BSE and he is hidden and probably sent somewhere for treatment. I also think that he is the masked child that the 2ML found in the abandoned house. We also learnt in these episodes that 4 children went missing. I think 1 of them survived the real BSE in the abandoned house and it's 1 of the twins. I think he is the one behind the initial calls and the fake teeth etc., The one with the mismatched eyes. Another reason to support my claim is that the mismatched guy received a message in the previous episodes from someone else reprimanding him as well as stating it was D-Day.
I also think that the BSE we have now and the mismatched eye guy could be the twins, instead of the mismatched eye guy being the real BSE. He kept saying I know him better that everyone else, i.e. twin behavior or something along the lines of what he has I want/belongs to me - showing jealousy between siblings.
Another theory is that the mismatched eye guy was tortured by the real BSE and went missing. The BSE we have now is the mismatched eye's twin and thus the parents took him in instead for some reason guilt or something else. However guilt is highly unlikely with the way the mother seemed to treat younger BSE and forcing him to eat sushi when he can't.
Finally I want to say that I don't think In-a is involved in the kidnapping & blackmailing because I don't see a clear motive on her part. Yes, she lost her hearing but Hee-Jo also stayed silent for her whether she wanted to or not, she also got her hearing back. She didn't want to marry the current BSE either because she knew he wasn't the real BSE or otherwise so it's not like she wants him back. She doesn't have much to be jealous of in regards to Hee-Jo anyway. Hence, why I concluded that she isn't involved however that doesn't mean that she is not a negative character she could fall on either side at this point, I think it will be negative.
In the episodes airing next week what i hope to see -
- BSE taking care of our girl and the colleagues being confused af about the change in his behavior and why he was acting this way towards someone he supposedly does not know. I don't want any of the characters to just outright say their relationship rather pieces that they put together and is an unsaid secret amongst them.
- I want a clarity on In-a's character is she on Hee-Jo's side or not etc.
- How is the child in the abandoned house related to this case. Is he the real BSE, which is my guess. It would also clear up who the mismatched eyes guy is. I hope one of my theories is true.
- I want to see some development between the main leads, in terms of talking out what happened and why its happening not just the taking care of our girl in the hospital. I hope their is communication.
