I started watching kdramas like half a year ago and i didn't even knew about this one (yes,i know,WHY?!) ,it was a recommendation and it was one of the best things that happened to me. I ABSOLUTELY DEVORED IT and loved it.
The mystery kept the drama going from the beginning and it kept me interested until the end. I kinda already guessed who was who but i was rooting for the other characters to find them on their own.
There were so many intense scenes that i had to cover my face with a pillow at 3 in the morning. The plot totally draws you in,the writers did a good job on being so meticulous with the details,and the kickass cast was AMAZING. I didn't like Seo In Guk in Shopping king Louie but freaking hell,his character in this drama was to die for. I loved him to pieces.

The romance tho...i have to be totally honest,it was a bit dry but i didn't even cared. The writers made the romance subtle and focused more on the thriller part.
Also i have to talk about the bromance,PARK BO GUM,you freaking made me cry. It was so funny to see all the characters mix together.

The ending left me with a couple of questions that i think everyone that've seen the drama knows about it...and it's been 3 years,so a second season it's likely not gonna happen,and that makes me sad. I'll miss the characters.

Definitely it's a must watch. 10/10!!