In this classic horror trope, everybody in a small town is in on a secret. The protagonist slowly begins to suspect something is wrong.
Game and Story Use
- Is there some sort of creepiness in your campaign setting that you just haven't been able to work in to the plot? Have the PCs stop for gas / dinner / the night in a small town. The trope is pretty strongly ingrained in our minds - one small hint (that things aren't quite as they seem in this quiet little town) will probably be enough to get your players to dig. Violently paranoid PCs might just torch the town to be safe.
- Great way to introduce a monster type (Dopplegangers, Vampires, Cultists, Brain Worms, etc.) that you've been meaning to use for a while, without it feeling forced. If a dragon just swoops over the city, the players are left asking "how come we've never seen one of those before?" If that same dragon instead lives in a cave at the edge of a creepy little town, and is fed virgins every season by the creepy townsfolk who worship and hide him, the players won't bat an eye.