I think that Troels, as a central character, is likely to be implicated. It would be really disappointing to find it was someone who we know nothing about or have hardly noticed.
If it is him, I think it'll come to light just as he's won the election. It'll cause maximum trouble, politically. Plus, it would be a fantastic scene, him raising his arm in victory, then seeing Lund approach him.
I still think of a look that Pernille and Troels exchanged, when she saw him in the police station. I keep wondering whether he knew her in a different way - maybe Pernille had joined that site and dated him? Oh I don't know!
I still think Charlotte's involved in some way, too. I can't believe that she'd see her niece talking to someone (in the white car) and not ask who he was. When she found Nanna in the hotel, why wouldn't she ask who it was that Nanna was seeing?
Why didn't the police find out who'd paid for the hotel?
Why has Bengt behaved in the way he did? Why did he visit the father of the kidnapped girl? Why did he not tell Lund about the necklace? Was that merely so that Lund would go back home with him? Surely if he told her, the case would be resolved quicker?
Bengt would be a good suspect in many ways. He's never there when Lund phones - why? He doesn't seem to have a great relationship with her son - has her son picked up on something odd about him (besides his hair?) He is right under Lund's nose and she hasn't suspected him. But then Bengt doesn't have any involvement in the political side, does he?