I originally watched this film solely for Lee Jong Suk. I'll admit right now that the concept wasn't really for me, but I was hoping that Lee Jong Suk would make up for it. I'm sad to say that he didn't. Whilst he was arguably the best part of this film, and he played the role of serial killer very well, his talent was wasted in a pointless, boring film that adds absolutely nothing new, and focuses on all the wrong things. The film focuses way too much on a dull detective, a dull plot and a dull execution. The best part of serial killer films and dramas, is the serial killer. They're the ones you're supposed to focus on, supposed to want to catch, the ones you feel tense watching as you see a game of cat and mouse unfold before your eyes. This film did none of that. In fact, our killer spends most of his time in police custody, doing absolutely nothing except smirking and occasionally getting free and then caught again. There's too many plot threads that go nowhere, interesting as individual ideas but horrifically uninteresting when paired as a whole. All but one killing is done off screen, and we are told rather than shown that our killer is a super bad person. I didn't care if he got caught, and I didn't care if he did. This film made me feel nothing for anyone. I didn't feel the scariness that others have said they felt, and I didn't feel anything for any character. Nothing happens that I found interesting, and I found myself on my phone during any part without Lee Jong Suk. The characters didn't make sense, and I didn't understand anyone's motivations. Our main detective was supposed to be this hardened, goes against the law when he has to, ying to LJS's yang who everyone was impressed with, but was a good guy really. Personally I found him to be meh. Forgettable and lackluster. The only scene with any sort of technical effort or cinematography was the first killing, and after that it's like the director gave up. I don't recommend the two hours spent to watch this film, and if like me you only want to watch this film for Lee Jong Suk, might I suggest watching any of the edits of him made on YouTube of this film instead. They do the same job in three minutes that this film tries to accomplish in two hours and twenty minutes. He's not in it anywhere near enough to warrant watching this. Boring, forgettable, pointless.