This is a non sequitur that has been nibbling on the edges of Hiro's mind for the last ten minutes: Laser light has a particular kind of gritty intensity, a molecular purity reflecting its origins. Your eye notices this, somehow knows that it's unnatural. It stands out anywhere, but especially under a dirty overpass in the middle of the night. Hiro keeps getting flashes of it in his peripheral vision, keeps glancing over to track down it's source. It's obvious to him, but no one else seems to notice.