I have watched all four seasons, and I can assure you that the second and fourth seasons are among the masterpieces of the Nordic Noir genre. Louise Bergstein (Natalie Madueno) is the main character in these series, working as a profiler assisting the police in solving criminal cases. The first season is good, but the real deal is the second season when the character Peter Hinge (portrayed by Tobias Santelmann) shows up. Then the third season has Alex Hogh Andersen from the Vikings series, but it is not as great as it was in the second season, but still, it is ok. However, the legendary season among all is the fourth season when Louise Bergstein faces her worst opponent. The last two episodes are almost like Sherlock Holmes vs Prof. Moriarty, so you should definitely watch it. The fourth season is awesome, thanks to two talented actors, Simon Sears and Swedish legend Dag Malmberg.