-An NPC merchant selling insects and other creepy crawlies-
"You want horseflies? Giant wasp? Gigmucc has them all on his cart, Gigmucc has a discount just for you..."
Captain Aubrey surveyed the deck of the captured sloop. He was amazed that such well run ship could crewed by such a motley gang of men. He turned to the doctor and wondered, "No man is born into piracy. What were these many fellows before they took up the black flag? Surely they can not all share the same story."
What if the innkeeper knew what you wanted before you did?
It is a small, lively town like so many others. Do you wonder who are the movers and shakers here?
After the PCs defeat (or force the rapid retreat of) a villanous necromancer/demon summoner, they discover a book. This book outlines how to summon a demon whose power increases according to the size of the summoning circle used to summon it. And after the PCs examine a map of the country, they find that the layout of the cities and roads match up with the required summoning circle. In fact, the final road that would complete the circle is currently in construction.
With anyone who can find out about the circle and the ritual to summon the demon able to somehow make the final road/line, and destruction of the cities and roads currently in existence out of the question (unless this is an evil campaign- that removes the moral quandary), how are the PCs going to solve this problem?