Every time I hit a roadblock, I feel like writing some thoughts down might help me; but I'm never around the computer when this happens. Today, I finally decided to jot down at least something, hoping that I'll be able to persuade myself one way or another.
So today's roadblock: What would prompt the main character to leave the 3rd city and go north? It could be: someone stole the crystals--but that would introduce a mystery toward the end of the story. The main villain could have stolen them. But how would the main villain also know where they are? It could be an unrelated reason: to catch his ride home? But he doesn't care about going back now as much. I guess I need to start thinking about what he wants to do, and then figure out whether going north would seem natural to the plot or not.