I'm a big fan of suspense/mystery dramas, so I thought of starting watching Gap Dong. Lee Joon also had a role, so this is a plus. Story: The story started fantastically good and went like that for many episodes. I could never be sure who the real killer was. I had many suspects, but I could never know for sure who he really is. The twists were also nice. The story of a copycat killer is something I have never seen before. What I liked very much is how they focused on two murder cases att the same time, increasing the mystery and interest. The truth was unexpected, something that made me like it even more. I didn't feel bored through at all, as situations keep changing in a interest way. Romance is not something that takes a big role in the story and I think it was perfect as it was. What I didn't like, though, is that some situations seemed too unrealistic and out of no where. I didn't find the ending that good, it could have been much better. Acting/casting: I have a thing for psychopaths in dramas, so Ryu Tae Oh became my favourite character right away from the start. Lee Joon did a fantastic role displaying his emotions and psychology. He really made me raise even more the respect I have for him as a whole person. His developement was nice and believable. I think he is a unique character, making me wonder what he may be thinking and what he is going to do next. Not your typical serial killer. It was the first time I saw Yoon Sang Hyun 's acting, and I must say he did a really nice job as detective Ha Moo Yeom and I could see the reason behind his actions. The one I didn't really like was Kim Min Jung as Dr. Oh Maria. Her acting didn't impress me and I didn't like her character, having an "alter ego" from time to time. Music: The music, from Every Single Day's songs to the instrumental tracks was excellent, fitting to the mystery and suspense atmosphere. I really like it. Rewatch value: I don't rewatch dramas. Overall: I think Gap Dong is a really nice mystery/crime/suspense drama for everyone who enjoys these genres and not only. It surely has its flaws, it is not perfect, but they didn't make me lose interest in it. It was worth-watching and realy nice, in my opinion.