A View to a Xill: peering out his window one night, a wealthy merchant, confined to a wheelchair, witnesses a Xill killing the youngest member of the royal family on the grounds of his estate while the young lad was on his way to court one of the merchant's grand-daughters. Now the Inquisition is coming to investigate.
He knows it was a Xill that did the killing, and he suspects it was done to put his house under a cloud of distrust that could cost it every contract it has- he never spoke well of the slain prince, after all- but he has no idea who would (or could) hire a supernatural assassin for the job.
Finding out who and why, and clearing the merchant's house along the way has become the PCs' job.