This is by far the best tv series I've ever seen in entire life. The level of drama, plot twist and adrenaline-driven is almost out of this world. Every scene is beautifully executed without redundancy nor typical meaningless Korean style. It is also emotional and has multiple level of meaning which drive me empty after finish watching. I rate 10/10 and would recommend it to anyone intelligent and fond of action-mystery-thriller-slight romance movie.
The series is quite long with me finished after 3 consecutive night, but it totally worth it.