Theories about the drama

 Pancake of the 7 Seas:

ah, looks like moo tae gu doesn't have any connection with this, but now bang je soo is alive, and that this season is definitely connected with the last season, i wonder how long this will take.

he might be connected with the 3rd season's killer Kaneki, who is connected to the second seasons killer

I think that season 5 will be about Kang center's past, why she has that special hearing? who is the " "CASE 2 " who has also a special hearing like Kang center?  Who is that mysterious woman? What is the secret of that hospital and Faber Lab? I think that Faber Lab has made experiments to improve humans' hearing and made that experiment on  Kang center " CASE 1 " and the other guy " CASE 2 " maybe he died or still alive, and maybe Kang center will search about him, maybe " CASE 2 " will have connexion with Do Kang Woo, Kaneki, Min, or even Moo Tae Gu because all of them have Mental Health problems, we can expect everything in Voice. It can be that " CASE 2 " will be the new serial killer in season 5.

Also, in my opinion, Derek will stay in Golden Time Team and find Kang center and the secret of Faber Lab.  

What do you think?

 eclOOO:

agreed, considering the case 2's name was japanese (i believe) most likely a connection with Do kang woo and or Bang je soo

I noticed that too, maybe Kang center will go to japan with Bang Je Soo and that woman  

 Pancake of the 7 Seas:

Do you think Dong Bang Min is also related to Moo Tae Gu? I mean, they might be together in the hospital...

Didn't he die. 

My opinion is the Fabre people is a criminal organization that assist the killers and when they get caught they just dispose of them. 

 Reesa:

Didn't he die. 

My opinion is the Fabre people is a criminal organization that assist the killers and when they get caught they just dispose of them. 

Oo this would actually bring things full circle, I always wondered about what happened to Moo Tae Gu because they overtly showed the whole scene to us. Maybe S5 will give us an explanation finally.

 Pancake of the 7 Seas:

moo tae gu was killed by a mob of psychopaths in the hospital, so why him? fabre might really had his hands on him when he was a kid, otherwise it'll just make season 1 far from the other seasons

His father went with him to get him checked out when he was a kid (after he killed the dog if i remember correctly). Maybe, fabre might have had connections with the hospital or just the doctors. 

Also just a theory but: Since Kang Kwon Joo and others were probably the first to be *experimented* on, considering Moo tae gu was similar age, they wanted to experiment with him but couldn't as his father was powerful in terms of politics and didn't want his own name to be tarnished. So they monitored him but when they did get their hands on him, he was too far off gone/could not be experimented with so they killed him. 

Although, considering how brutally they killed him, there seems to be some sort of emotions involved so the theory is probably absolutely wrong

 Kwangnoi111:

I think dong bang min might even show up in ss5, he could be the key to next season, because he just got caught. And it has to be about Fabrelab, he and Kang kwon joo had been tested before. Like Min knows something? Because the hearing aids he used were like they were from Fabre. He also attended the same school as Je soo. And the tattoo he said was the last game too.

True, and then, maybe Derek reluctantly teaming up with Min could become possible...