I dropped "The Veil" with the same genre, simply because it is reusing the same plot and character of spy genre, most annoying part however to reuse the same scene over and over again (scene of the ML partner died). it is worst-lazy-possible-way to make a filler.

I compared to The Veil because this drama deserve better rating.

Story is solid; since it is an adaption from BBC series so I kind of expect that.

Acting is overall good. Oscar go to the main villain; the guy is genius potraying the character with more expression but lesser line. Silver medal goes to female lead, I watched few of her works. I don't really like all of them but impressed with her role in "Miracle that we met", sit her nice on role of a-hot-mother-in-her-prime.

Character. For series character development is more important than the story it self, and female lead fit the bill.
It is enough characters of pure evil, butt licking, betrayer, change of side, is a must-twist-ingredient for this genre;