A delectable chrismas classic - Now with mayhem!
The wide wicked world is a very dangerous place, especially for not-quite so big leeches who wish nothing so much as to be left out of thing such as wars, and wizards, and spells.
The player characters, experienced and somewhat well known, hear rumors and travelers' tales about a distant area being overrun by dragons (or other terrifying monstrosities). The locals have sent them a message, begging for heroic aid.
When they investigate, they discover that nothing of the sort is going on. It turns out that a group of thieves wanted them out of the way so that they could rob them (or someone who would normally receive their protection).