For me, this drama was a very pleasant journey. Generally I love these kind of dramas so the story was enough to get my attention. The acting was really mind blowing from the male leads, especially the character of Ryu Tae Oh. Lee Joon has portrayed the mad, twisted and crazy guy so perfectly, honestly I was freezing to death when I saw his expressions, that look in his eyes and his so creepy smile, that moment when he from totally serious face slowly begins to smile, uuf, it gave me a chills every time. I would give a ten only for his acting. There are flaws in this drama of course, the main flaw was how the female leads were annoying in trying to understand a psycho killer without emotions or humanity, I mean I would kill them or torture them or any other way I would think to do except that one, to understand them or help them in some way. I get it, Maria was a doctor so she had that side naturally in her, the other one was just a high school kid, so naive and good, but either way it was crazy to try to be on the side of the lunatic killers. Also, I liked the character of Sung Dong Il, one of my favourite older actors, he truly knows how to act, I enjoy every time I see him. What I liked the most is how they made comparisons to the movie Silence of the lambs and Hannibal Lector (which is one my favourite movies) and to the book "Crime and punishment'" which is one of my favourite books, it was such a great idea for all that, it fitted perfectly in the whole concept of the story and characters. Overall I liked the drama really and in some weird and sick way I was sad at the end and I really loved Ryu Tae Oh's character, not that I felt sympathy or something like that, it's just that I was fascinated by the sickness and craziness of his brilliant mind. Gap Dong as the main culprit became really like a myth, exactly like Jack the Reaper and the actor who played him was great. Music was so good, I liked the main song, it was full of action and emotions, it didn't bother me at all since it was played many times in drama. Who loves dramas with thriller and obsessed concept with many twisted characters and lot of excitement, this one is definitely not to miss. Although the story is slow and they could easily finish everything with 16 episodes, I was satisfied at the end.