Vary exciting Thriller/ Crime drama as expected from OCN. New idea and an unexpected Killer and a great build up to the idea they want to give in the end. even tho it get a little slow in the mid and i got frustrated by other crimes getting in the way from the main one but it was to be use in the end, So i was AH WE NEED IT i though it was just to full the time but it wasn't.
Everyone has an agenda and work to catch the killer for his own good not bc he is killer a lot found that frustrated but i found it the most excited and new thing about this drama, not selling the great cops fighting together to catch the bad guy , people are full of flaws like this. and all want to hide their own flaws. the one without agenda or flaws were the young fresh who want to be great cop and are used by the other that's so realistic. I know that most take it as crime and focused in catching the killer but the main point in Hyun Jae , Hwa Young and soo young characters and what we saw in those characters.
The writer made use of the Cha Soo Young (FL) power and it didn't come off or super clingy and her character was well made for me. also i loved Soo Young acting.
Janghyuk as always choose new character that no other actor can showcase like him and give amazing acting that i was totally fooled in the start. the drama is all build around him when i lose interest in couple of ep Hyun Jae was the one holding me to the drama, the character is that strong i hate it sometimes but i understand he is psycho too .
The killer i was sad he is the one TT but honestly i was amazed by his acting when he change his character completely. so it was amazing that it was him. all psychos are amazing any way lol.

over all a really good crime drama, i give it 8 bc i lost interest a little in some eps and expected some plot if not i would give it 9.