Very often we will have the impression of having reached the end of the task, because we will find (or they will bring us) similar hairs of the one we seek; but since it is not known of any case where a hair has a knot in the middle without human hand intervention, we will almost always end up with the knot in question being a mere thickening of the caliber of the hair (although we do not know of any similar case) or a deposit of some silicate or any oxide produced by a long stay against a wet surface. It is probable that we will advance in this way through various sections of major and minor pipes, until we reach that place where no one will decide to penetrate: the main drain heading in the direction of the river, the torrential meeting of detritus in which no money, no boat, no bribe will allow us to continue the search.