Mindy McAdams I agree with Kyla Squires - the author is setting us up for the next book, and really, I don't need to see any more of Valentin. Ugh.
This answer contains spoilers… (view spoiler)[No, there isn't a plot hole. It's revealed from the stadium footage that Valentin isn't has an alibi for the night of one of the killings. So he's dropped as the main suspect. Valentin is used as a red herring to misdirect the readers. And it's quite possibly Nesbo will return to his story in future books. But as far as this story is concerned, that doesn't make for a plot hole. (hide spoiler)]
Lazar Jovanović Everything is in place. Valentin was a good misguide for the characters inside the story as it was for the readers. There is deffinitely going to be more of him in the following books...