I head to Riften by way of Ivarstead. On the other side of the river is a seemingly abandoned farmhouse. I head over there to see if there is anything interesting, and I find some demented tramp, Narfi. Narfi is actually the rightful owner of the house - it was his family homestead, but his parents died some time ago. Now Narfi spends his day waiting for his sister Reyda to return. Some time ago she went off to gather some ingredients for something, and never returned.
I ask the innkeep about this, and he corroborates the story - but adds that it is generally assumed Reyda died, but no one had the heart to tell Narfi in his already sorry state of mind. There is an island in the river not far from the town that Reyda was wont to often gather ingredients, and one day she didn't come back. There is a crypt on the island, Giermand's Hall, and the townsfolk figure some undead being came and offed her.
To me this sounds like an incident.
My guess is, though, that Reyda just drowned one time in the river. Ghouls don't make habits of randomly coming out of hiding.
With the remains I find an amulet that looks unique. I take this back to Narfi and let him know the bad news.
There's something definitely fishy about that Giermand's Hall, though. I go to investigate.