First of all it's worth mentioning that it's a story based on real events, however the ending of the story is speculative, so the authors try to fit all possible versions of what happened to the group into a working narrative.
The filmmakers did a twist with this show, the story is told in two parts happening simultaneously, so you have half of the episodes as a criminal investigation show and the other half as an adventure/thriller. The
thriller part is presented in black and white simulating the style of the old soviet Cinema, while the investigation/crime part is coloured.
The acting is decent, it reflects the era very well and there are a lot of unexpected plot twits on the way, overall not a bad show at all ...