Something catches his eye out in the darkness beyond the window. The train has reached one of those parts of the Underground where dim gun-barrel-colored light sifts down, betraying the stygian secrets of the Tube. Everyone in the car blinks, glances, and draws breath. The World has rematerialized around them for a moment. Fragments of wall, encrusted trusses, bundles of cable hang in space out there, revolving slowly, like astronomical bodies, as the train works its way past.