... are an excellent thing, if you want to read (or write) something by the way, eg. Waiting, without having to start a book that you might not even finish reading. For aspiring authors, it's a great way to implement ideas and try them out.
If I have a trailer for a novel, I like to sit down and write something short. That clears my mind and I use my time wisely. Within a few days I wrote my first short story as a "stopgap", my novels have a completely different quality.
Just in the underground? Not at all. Look closely, it can lurk everywhere and anything there for you. You do not see anybody? Does it come from the dark at the very back? Maybe it's not a human being at all. Look more closely, nothing is as it sometimes seems. Maybe there is something on the bars above. Maybe something is wrong with the puddle. Whatever it is, you will not get out of here ... or will you ?!