This show is amazing in the way it deals and shows disorders, psychiatric issues, and many more. I love how it shows the rawness strangeness in the way some people behave because of problems they've come upon in life which results in the flaws of their personality/attitude/behavior. 

I wanted to discuss and see what other people may think or theorize is MY's mother's reason for being the way she is. I'm sure that future episodes will expose or hint to as to why MY's mother acts and behaves the way that she does from the clips shown till ep 13. 

If you have not watched ep 13 .... SPOILER ALERT BELOW!!

This is my theory.....

We've seen the mother display fierce possessiveness over MY and a strong need for control over her and her own husband. I definitely believe she is unstable but not in the conventional sense where her unstable-ness is obvious through her actions or words. She seems to have a warped view of how the world revolves and of life. She is obviously capable of great manipulation and to lie. But she has a very good control over herself, enough to deceive those around her as she takes on a whole other persona and keep to it.  It's hard to act and be someone that you are not.

At the end of EP 13, we learn from the mother that the word "psycho" was derived from the original Greek word, psyche. I believe that MY's mother suffers from a severe case of psychopathic tendencies. This could be obvious to some people but maybe not to others though. 

The reason why I think MY's mother is a true psychopath because: 

- She lacked empathy when killing KT and ST's mother. Lacking in remorse for her actions, though it caused pain for others, as she sang a song and paints her nails. 

- Psychopaths are excellent chameleons as well. They have an acute ability to understand their environment and blend into the woodwork as if they have always been there.  Such as the case when she posed as the head nurse. If this weren't a drama TV show and you worked at OK Psychiatry yourself, you'd probably never guess or suspect.

- Sometimes, psychopaths regard people not as human beings but toys. In which to manipulate to further their own agendas/benefit or, sometimes, for amusement. But most times, psychopaths often manipulate others to benefits themselves without regard to how it affects others. MY's mother toyed with ST with symbols of butterflies and leaving note at MY's house that KT found. She also manipulated and toyed with the director most likely to veer the suspicion that MY's mother is another patient instead of her.

There are several other things that I noticed that leads me to think psychopathy as well, but the above is the short list.

Unfortunately, psychopathy is not caused because of childhood or past trauma. It  is a risk factor that past trauma can cause psychopathy to develop later but there's stronger medical evidence that it's an inherited trait from genetics. Psychopathy can also be caused by brain injury and the mother did fall down from the second floor after being pushed by the father, but she definitely exhibited psychopathic traits before she fell. So, it's unlikely that a brain injury caused the mother's psychopathy. She most likely was born like this and inherited the psychopathic trait from genetics. 

But one thing I do think is that the psychopathy maybe slightly exaggerated for the sake of entertainment for the drama. Unfortunately, there are psychopaths that live in this world (but only 1% of the general population) and are not believed to be the serial killers or homicidal aggressive people TV shows and movies have shown them to be. A lot of them have families, have jobs and live a normal life and are not aggressive. Some can be though but not all. Fun fact (or not fun, depending on how you look at it) most psychopaths that live among us are usually executive businessmen or high-powered CEOs. Most enjoy being in the business world because their tendencies work and can succeed best in this often cut-throat environment. Some can also be believed to be in the government as politicians because they want to be in the spotlight and be admired. Their skill for manipulation and often being well-versed in persuasion fit right in. 

What do you guys think? Agree? Disagree? Thoughts?

Also to note, if it's true that MY's mother is diagnosed as a psychopath then it would also explain why MY herself  is diagnosed with anti-social disorder. A parent being a psychopath with the degree of manipulation they often carry and enforce can definitely cause anti-social disorder in MY.

Anti-social disorder can be caused by unstable, chaotic and neglectful behavior from childhood or past. It's not the sole cause but just one of them. 

Disagree.

My theory: 

MY's mother is  innocent but yes, she has mental illness. The book she wrote doesn't have ending chapter yet. She depressed because the last chapter will reveal everything, including the murderer.

The butterfly was stolen and used by real culprit when murdered the brothers mom.
This is the only way MY to accept that she's not the monster her mom used to say and the brothers will find the real culprit.

Let's find out next week.

The mom and the woman in the tunnel really look alike. The eyebrow, eye, nose, lips, teeth., the crazyness...  looks the same person so it is probable MY's mom killed GT and ST mom.

I agree to the original post but only to some extent. They say somewhere along the lines that the mother came from a very wealthy family of physicians (including her siblings, parents, cousins, etc.)  but suddenly during her third year of college she suddenly dropped out, cut all ties with her family and replaced a knife with a pen and began writing. She then moved on to marry FL's dad and have her. 

I think she's always had the psychopathy in her and may have always had problems viewing the world as others did. She clearly knows how to pretend to fit in though. I think a family like hers would have been especially tough to grow up in - with pressures of being success and the best at everything and all that. I also think she would have always felt entitled to things, being from such a wealthy family as she was. I think she may have shown signs of her psychopathy by lashing out at people who acted in ways and did things she didn't like as she grew up but, as it often is in most multi-generationally wealthy Korean families, she most likely always avoided being punished for her behavior some way or another.

We also know that she was extremely beautiful and extremely vain (also very narcissistic). Plus, her behavior after killing their mom wasn't in any way that of someone - even a psychopath - who has killed for the first time. We know that she's very good at hiding her crimes too - as we saw with the patient that went missing and was never found but that she also made clear would never be able to return. 

My very strong suspicion is that something happened to her during that third year of college - there HAD to have been a trigger for her to take such drastic actions - most likely a sexual assault (something where she would have been made to feel powerless), which her family may have wanted to brush under the rug. She's clearly very driven to not ever feel weak and finds power in doing so. I believe she sees her family members as being weak and pathetic and suspect she may have felt that way about herself during the assault but then with the way her family likely responded she finally just snapped. I believe she secretly killed her abuser and completely got away with it. After that first kill she likely felt so empowered by it that she fully embraced her psychopathy, believing her different way of viewing the world as being her strength to see what others couldn't. 

I think that's why it was so easy for her to kill over such a small (and inconceivable) thing. She believed she didn't have to justify her behavior to anyone because people just weren't at her level in terms of understanding 'reality' (or her warped version of it). 

I believe she also recognized a familiar presence of psychopathy in her daughter (possibly due to her lack of affect since an early age) and believed she could mold and teach her the way to attain 'the next level of understanding' as she seemed to view it, without having to go through whatever it was that finally made her embrace hers. In her warped ass mind I think that was her way of showing her love. Had the FL grown up with her mother she very likely would have become just like her (as we saw with the way she responded to the injured bird, which lead to the death of the brothers' mother). It's the good old nature vs nurture argument. Her nurturing would have been the deciding factor. You could clearly see that she didn't realize then that what she was being taught was very, very wrong. By her mother disappearing so early on, she gained a greater chance at being able to find the right path instead of learning the wrong one. 

It's almost like she was in limbo for a long time. Then meeting the publisher was her first stroke of good luck in strengthening that metaphysical pull away from full-blown psychopathy. Then the more good you introduced into her life the stronger that pull became. She was very childlike in her approach to learning how to be...likeable. She yearned for it and tried very hard to get it right. She just needed to be guided. One path, fed by fear, would lead her to become like her mother but also accepted by her. The other path would lead her to be liked by people who she felt drawn to. She wanted to join them but didn't know how and also knew that doing so went completely against the will of her mother. So it was like making her choose between her mom and her own happiness. 

Anyway, that's all just my opinion after a very long time dwelling on this. It drives me crazy that we don't know why she suddenly dropped out of college, cut ties with her family and started writing.