Christmas type holiday that can be thrown into any city/town.
The addition of “irrelevant” details adds local colour to a campaign world, giving the impression that the DM has thought very deeply about the history of even the smallest architectural feature.
An adventuress, Semma, has returned to her home village, but something has gone badly wrong: it's the furtive glances, the conversations that stop when she approaches, the childhood friends who now have no time for her. She returns to the town or city and enlists your party to help her find out what's going on.
The party must find out what is wrong: something (perhaps a Cthulhoid monster, perhaps a gang of vampires, perhaps just a bunch of bandits) is extorting obedience from the villagers by threatening their loved ones with at least death. Once the source is discovered, Semma and the party and a few brave yeomen (and women) must deal with the threat by finding its base and defeating it, and then deal with the remnant corrupted villagers who willingly served the Evil Force. These may prove to be the most difficult foe...