As it vanishes once more form his senses, he finds that he can trace the thin line back, ever so slightly; a web of insects dot the room, more than two dozen; a spider here, a gnat there, a fly in one corner, all tiny, virtually unnoticeable, even to his perceptions, and all such a common part of life elsewhere, that even the most trained eye is likely to pay them any heed. They seem to be a self-contained network, and not linked to anything outside, but that could easily change, if one hitched a ride on a departing passenger, likely the same way they arrived. If he invests a bit of energy into following the trail, which, unfortunately, is likely to destroy the gnat he's holding, he'll also find that they seem to be storing information; bits of overhead conversations.