I just found Troubled Blood was treading water for most of its entire four episodes. It should had remained a two parter.
I guess JK Rowling put all the anti Trans stuff in the book as it was the only way the novel would be talked about. Going on the maxim that there is no such thing as bad publicity.
Strike and Robin think that Dr Margot Bamborough had a suspicion of a serial killer operating in her area. Maybe Steve Douthwaite was the man they want and Strike had traced him living up north under a new alias.
It ends with an overlong confession. It had to be overlong as the murderer had a lot of deaths and attempted deaths to reveal.
It was the perkiest part of the episode. To think viewers had to endure all kinds of red herrings and blind allies to get to this far.
At least the killer was unrepentant and thoroughly despicable.