Things to do in Diesdorf When You're Dead

From the introduction:

On travelling the road between Altdorf and Nuln the PCs stop in the small town of Diesdorf. But during the night something strange happens, and one of the PCs wakes up to find himself a ghost, detached from his dead body! The PCs are going to have to find out what happened, and whether they can get their companion’s spirit back into his body. But first what are they going to do with his corpse?

Their investigations will eventually lead them to someone messing around with the spirits of the dead. Will they be able to figure out how to reverse what they have done? And how will they deal with the unwelcome presence of a dangerous Witch Hunter?