* spoiler * WHO IS THE CURRENT SERIAL KILLER?

from the looks of it, JBR is the son of the pregnant woman who said her husband had died in an accident but she'd found out her son had the psychopath gene or something (there was a picture frame of them on the side when he was at home). either he is likely to be triggered by the latest recent events, OR.. there's still a chance he could end up being the "genius?" since they kept mentioning how the only other people who have the gene are geniuses. Or it could be that there was a switch at birth... lmao so many theories.

I think though, there's more to it than the Doctor being the Serial killer and that's that. There was also someone at his home when the grandma turned up to do the cleaning (I don't really know who that was?)

So many theories tho, and I'm intrigued to see what the accident will do to JBR.. I'm worried about the grandma too tho!!

I will break it down to you guys but no drama reveals killers on first eps. Usually it is like bait for us to get fooled. I bet doc was somehow involved maybe he wants some kind of answers himself and that is why he so far appears suspicious to us.

Tho possibility of few killers is good too ngl.

Right now I'm most suspicious of Jung Ba Reum, since he's appearing near the crime scenes, that's  at least three times now.

And of course the Priest because of the anti religious elements and being disabled, nobody would suspect the priest, but that also makes it the perfect twist of sort.

But yeah so far the show has made a great job making you second guess everything you see. 

I think both of them are hiding something.. Right now, I'm even questioning weather all the killings where done by the same person. Some have missing fingers and some haven't. Also, we can't forget that there is another one with the psycho gene.. Right now, the series has me hooked! I can't wait for next week!!

I believe that there are two killers, but not work together.

 euler holanda:

I believe that there are two killers, but not work together.

I believe so too.

1. Jung Ba Reum is the "Cross" serial killer, but he's not the one who hurt Chi Kook or put his watch on Mi Jung's body in the vineyard but that's Sung Yo Han's doings. Sung Yo Han has been following Jung Ba Reum with his murders, and he knows who the predator is. That explains why he also had the pictures before the police because he was there when the killings took place... I think Sung Yo Han is trying to trap Jung Ba Reum with his own ways...because maybe he's been holding grudges ever since they were high schoolers. He probably put Chi Kook's watch there to trap Jung Ba Reum because the last person to meet Chi Kook was clearly Jung Ba Reum. 

So, why did he kill grandma?  My theory is, Sung Yo Han knew who Grandma was and her relationship with Jung Bareum from the beginning she entered his house. When he found out Grandma took the picture, he tried to stop her from giving it to Jung Ba Reum because it would reveal his identity to Jung Ba Reum. It would fucked him up if that happens. Other than that, he doesn't want to be accused of being the "Cross" killer when he's not, he just wants to get his revenge with Jung Ba Reum. (We can see bloody faced Sung Yo Han in Ep. 5's trailer, and he's wearing high school uniform)

Did you see Sung Yo Han's face when he walked out from Jung Ba Reum's ward because he saw Oh Bong Yi crying? That's a face of satisfaction when you get your revenge done. He's trying to kill these people around Jung Ba Reum... Chi Kook, Grandma, those who are close to Jung Ba Reum.

Why did he kill Danielle Lee? Are you sure he's the one who killed Danielle Lee? We didn't see the killer's face for sure but we knew Sung Yo Han is the one who disposed the body. If Sung Yo Han is the "Cross" killer, his M.O (Modus Operandi) should be the same. Middle finger to the cross. But in both Grandma and Danielle Lee cases, it's not. Plus, he's super sloppy with his works.

2. My second theory is, Dun dun dun!!!

At the beginning of Ep. 1, we can see a mouse fighting back a snake. Jung Ba Reum is not a typical, submissive mouse. He's probably already batshit crazy as he is but after the grandma murder, he's determined to fight back the snake just like a predator. So yes, we are going to have a Dark-Hero in this drama if my first theory isn't true! Jung Ba Reum would eventually explore his psychopathic side (if he didn't already do that before) and probably make a 'show' of pretending to be the Predator. The ending of Ep. 4 might be Jung Ba Reum's secret idea and perhaps Ko Moochi, Choi PD and his friend don't know about this. Jung Ba Reum acted alone. He has a psychopathic gene so he knows what the other killer hates the most and he's willing to do the extremes to catch the killer. 

Posting it here for discussion 

The more I think about it the more odd it would be if the whole thing is staged. Provided that the call is real. The killer stated that if MC can’t figure out the patterns, he will kill the kid and show the whole world which mean live-streaming. Then what’s the point of Ba Reum coming in to lure the killer when the killer already stated that he will show the world himself?

The killer is willing to show himself so why is there a need for Ba Reum?
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If the real kidnapper see the stage kidnapper wouldn’t he knew 100% it’s fake?

@thefoooook 's theory make sense, but I'm wondering if Yo Han was truly the one who killed the grandmother. I I think he wasn't the one who killed her, he arrived after Ba Reum because he was looking for the granny and almost got caught. If he was the killer, he would have escaped after his killing, why would he risk to expose himself like that? He ain't stupid. It doesn't make sense to me. I'm sure he didn't kill Daniel Lee, he was just following the killer and just threw the body after the killer left it. Why did he throw the body though? 

Yo Han is following Ba Reum, but why would he kill the people close to him? He could have been the one who hurt Chi Kook because if it was the real killer, he would have just killed him. But he kept him alive. Now that I'm writing this... what IF not only Yo Han is trying to trap Ba Reum, but he joined hands with Han Seo Jun? Like, HSJ thought Yo Han is his son, maybe Yo Han told him that he isn't his son, but he knows his real son aka Ba Reum. So that's how they planned the thing with Chi Kook, that's why Seo Jun appeared just in time to help Chi Kook because after all, they didn't want him to die for real. 

Someone here said that P.O's character might have psychopathic gene and you know what? It makes sense, lol. Because his character looks so pointless so far. And I also think that there are two psychos and one genuis. Yo Han is the genius, which leads us to the fact that Ba Reum (most likely) and someone else are the psychopaths.