Generally he knew by instinct the likely length of an investigation, but on this occasion he did not: as he fought to get his breath he suddenly saw himself as others must see him, and he was struck by the impossibility of his task. The event of the boy's death was not simple because it was not unique and if he traced it backwards, running the time slowly in the opposite direction (but did it have a direction?), it became no clearer. The chain of causality might extend as far back as the boy's birth, in a particular place and on a particular date, or even further into the darkness beyond that. And what of the murderer, for what sequence of events had drawn him to wander by this old church? All these events were random and yet connected, part of a pattern so large that it remained inexplicable. He might, then, have to invent a past from the evidence available - and, in that case, would not the future also be an invention? It was as if he were staring at one of those puzzle drawings in which foreground and background create entirely different images: you could not look at such a thing for long.