I am usually pretty picky when it comes to TV series. I suppose I have very specific tastes and while I realize that 99% of them are fiction, I really abhor when writers don't even try to make it plausible.
This series is a REAL Gem. Here are the elements they have. Please keep in mind that I watched it in native Russian and subtitles don't do it justice. Not only they miss all the nuanced jargon but also larger parts of the story where say, they say 'ludi' which translates to people, and implies men and women, the subtitles say men.
Here are the strong points:
1. Costumes, mannerisms and writing are all on point. It's really shows up well in the first episode of the Arina character and then throughout the series at a more subtle points.
2. The story is complex and layered. Nothing is as it seems and most of it is plausible.
3. The NKVD and the ussr military leadership are portrayed very accurately. The blackmail, quid pro quo are all accurate and very believable. They rarely gave anyone benefit of the doubt and only pushed their own agenda.
4. The actual spy craft is very good and very detailed and many times it's explained why certain things are done and most of it stems from human nature. In american movies that's very rarely done.
5. There is enough character development to really create a bond with each of the main cast and to try to understand them. They all are portrayed as smart and very good at their job, yet they are very different. Some are very honest to the point of naitette, while others while being very patriotic, realize that the world is not black and white and most of the time, you cannot get your way and that in order to have better chance, you have to be flexible and adjust on the fly.
I only have one negative:
1. No additional seasons. Boooooooooooooooooo