Darkness: Those Who Kill
I didn't see how revealing a major identity in the first episode could be sustainable as a thriller for seven more, but they just about got away with it.
However, this was reliant on some major holes in the plot. Alice makes preparation for an entrapment and yet is totally unprepared come the time. How did Peter find the knife in the water in the dark amidst a furious fight?? Sloppy.
Season 3: Lost Those Who Kill
The first four episodes were good and essentially revolved around a single storyline.
The last four episodes is set three years later and introduces a new storyline with a thread running through from the first four.
The new story is poor and the actions of Louise are in no way credible. She is supposed to be a profiler, but she acts like a cop and goes places where in reality she would have no access to.
She is also paranoid about being stalked, which is a throwback to season 2, but she still goes alone into dark/derelict buildings and walks into her flat and leaves to her apartment door open behind her.
Season 4:
Once again Louise is far more involved in everything than should be as a profiler. It became really irritating.
The appearance of Dag Malmberg really set the alarm bells ringing. Was this a throwback to the days of Morse when the guest star was always the murderer?
The story didn't hand together at well, it was almost like they made it up as they went along.