This is a strange program -- all the ingredients seem to be there for a good show but it doesn't get there. Part of the problem is that the plotting is twisted and hard to follow, part of the problem is that the characters aren't very well developed, and part of the problem is that the writing is overly cliched -- way too many "'let's go get 'em" and "there he is!" and "this is an important case and we must do our best" kind of lines.
But the other issue is the strangest -- for whatever reason, the camera spends far too much time focused on James Nesbitt's face, as though the storyline depended entirely on his expressions. He's a good actor but do we have to watch him so closely, follow his every facial tic, watch his eyes watch other people? It's almost as if someone said, "hey, let's do a show about James Nesbitt's face and, sure, we can add some plot and some characters if you want." Weird.