Comment by trhway

rats have ultrasound hearing, and children have higher range of hearing than adults, though not in ultrasound. While i don't subscribe to the literary version of a piper taking children away, it may have been noticed by the people back then that animals and children hear some flutes while adults - don't. (An example of a gruesome speculative version of events would be for example that it was used to sort "good" children say from "possessed", especially if children playing in the dirt/etc. were noticed to have say higher infection rate) The story don't mention nor dogs nor cats reacting to the piper, and that is natural given that it is a rat infested medieval city - getting rid of dogs and especially of cats (done back then for superstitious religious reasons ) would be the major way of getting into rat infestation in the first place.