Both sides in the game

It seems Swedish officers made a terrible mistake 15 years ago and sent an innocent man to jail for of murdering a girl! Someone must go to the bottom of this, the police have to admit they've been all wrong and find the real culprit. Or are they wrong yet again and thus a laughing stock of whole Norrland's community. There have been two movies before and the season 1 as well - and it's still pretty fantastic.