In that same antediluvian period which gave the Inspector’s building its wakeful neon ornamentation, police investigators had pinboards on to which they would physically fix pieces of paper to assist in visualising the flow of cause and effect and the interactions of persons of interest. It seems to Neith to propose a very linear perception of motive, and to make heavy work of the layered and often conflicting patterns of human deceit. Modern methods, of course, have improved it: she still has her crime wall, but it is projected on to the sheer plaster of her home, the information itself held in the System. Any individual document on it may be searched or tagged, so that she can at will select any part of the wall and make that part the top of the tree, watching all the others fall into strands and tangles of bad action. "Turn the case on its head" is an old standby for a copper in a jammed investigation, but only recently has it been an option to be selected from a drop-down menu.