This is a very underrated show. This is the best show i've ever watched. It is fully action packed, and there's plot twists regularly to keep the show interesting. There's some romance too.

The show is about Cha Dal Geon wanting revenge for terrorist attack plotted by a company where his nephew dies in the plane, but the entire government and NIS is corrupt and covering it up. So, Cha Dal Geon, along with another NIS Agent, Go Hae Ri, is trying to expose everyone behind the terrorist plane attack.

There is lot of interesting politics too. In this show, allies become enemies and enemies become allies. I highly recommend it to everyone.