It is a drama with great casting, excellent OST and a masterpiece story dealing with the agony if being a monster is in born or developed due to its environment. I loved how the writer gave a solid plot in the beginning making you realize that you already know the whole story, but it's not. Each episode is something you will look forward. Characters are being slowly and well introduced in each episode.Their backstories are well put up together that you will feel, sympathize and understand their actions, even it's good or bad. In each episode, secrets are being revealed and memories forgotten are slowly remembered. Even each case and crime stories aside from the main plot are well written.Mysteries in this show, like who is Min and Joon Yeong, can be easily guessed, however, the writer never failed to surprise viewers with different point of view and unexpected scenarios. I loved all the actors. I intentionally watched it because of Seo In Guk. But as shows goes on, you will love all the characters even the extras (the victim and culprit) from each crime. I was also surprised how D.O. acted well here. I must admit the two villain here is the main recipe of the show. If you love romance, I can say that this show had only few of that. Even the story involved a man and a woman, the relationship of characters of SIG and Jang Nara are more on trust and their importance to each other which slowly build throughout the show rather than cliche' romance thing. However, the lack of romance was compensated by its superb Bromance (Brotherly Relationship). Hope to see both In Guk and Bo Gum again in another show. In totality, this is the show you will surely remember. Highly recommended.