The Inhuman Condition is a novelette written by Clive Barker. It was first published in the 1985 collection Books of Blood, Volume IV.
Plot[]
A young man named Karney and his friends beat up a vagrant for fun. Karney steals a strange knotted piece of string he finds on the vagrant. A keen fan of puzzles, Karney undoes the knots that evening, not knowing that in doing so he is releasing a succession of demons who proceed to kill off his friends. The demons seem progressively more advanced, appearing to evolve with each knot. When he realizes what he has done, Karney has to seek out the vagrant for help.