In Rebel Without a Chance, the characters come across a halfling village where many of the residents have been mentally dominated by a half-orc that they rescued. The remainder are trying to free themselves. The dominated residents will try to get the characters to leave the village; if they stay, the characters will not know for certain which halflings are affected, and therefore potential enemies.
This was one of the earliest adventures I wrote for this series.
The villain in this one is quite clearly an evil mentalist, if not by profession then by deed. You can set the level to create a suitable challenge for your players.
Referring back to the recent post on Murder Hobo PCs this adventure hook has the nice twist in that almost everyone thrown against the party is a completely innocent halfling controlled against their will.