So the unnecessarily convoluted story is not what makes it bad. It could be improved, but considering other RTS TV series it is OK.
What makes it bad is the acting. It is just so terrible. It is catastrophically bad. I can't believe the lead actor even went to acting school, let alone that he was cast as the lead in a major TV series. He's just so wooden.
The casting of the entire series is unforgivable.
There are a couple of great performances by some seasoned actors that appear in the series, but all the young actors are terrible.
The lead actor is particularly bad. The actress who plays the forensic investigator is also very bad, along the lead's partner Mirko who is just a little bit better than the lead, but still very bad.
I googled those three actors they all seem to be children of important people in Serbian theater/cinema. Nepotism is the only thing that could explain the terrible casting. Either that or the casting director was blind and deaf.
