Good action and good investigation sprinkled with suspense and thought deeper than the first glance is exactly what I search for in a good drama and this gave me exactly what I wanted and more. I stumbled upon it accidentally - by clicking on the OST MV on YouTube - and then I noticed a familiar face - Park HaeJin - and as the MV impressed me and I adore Park HaeJin because of "Doctor Stranger" I gave the drama a try and it didn't disappoint me a single bit. Each character was crafted carefully - from visual to the inner world and reasoning behind their actions and decisions they make. Why an assassin is and assassin, why a gangster is a gangster, why a psycho became one and most importantly - why they all want to become human again, after being beasts for so long. Each and every actor fit their character flawlessly and it seemed that all of them still have a lot of stories to tell and that, to my mind, is important - that a character seems so rich, so full that you have a feeling it can tell even more than the scriptwriter has presented. The subtle (and not so subtle) connections between the said characters that allowed the story to grow and evolve, filled each episode with suspense and anticipation for what will happen next. Who has killed who and why? How is he connected to him? Did he really do it? All those questions run at least through my head and I received an answer in each following episode, getting more questions as an addition. Apart from the way that the drama made me think, I also loved the idea that even beasts want to be and can be human, that some beasts are only circumstantial and might not even be the ones that should be feared, that people we trust might be scarier than a beast hiding in the dark. No beast is ever as scary as human - human is the scariest person on earth no matter how we look at it. The plot playing with monsters and humans, who turn to be the true beast, was captivating and I literally couldn't stop watching. The investigation done in extraordinary way, the perfectly choreographed action scenes, the raw and realistic feelings of friendship and trust that grow, get stumbled upon and the re-emerge, and, my favorite, basically no romance that would interfere with the story. This is joining my top favorite dramas and in all honestly I need a season 2 with the same cast, same characters and new human-monsters to catch. Give this drama a try - I guarantee you won't regret it.