From publisher blurb:
In Hereditary Wickedness, the characters visit Straton. A small thriving town ruled by the Strats, a family with a long history and a good relation with the crown. The characters ignore what they are about to witness. Maximilian Strat, the current ruler's predecessor, made a deal with a devil about a hundred years ago. He wished for his family to be strong and cunning, so the devil added a little of his blood to his. Today, all of the Strats foster a little devil's blood within their veins, and a devilish possession is about to occur.
This Shadowdark adventure brings the heroes to a town that is about to be taken over by devils. The characters experience strange phenomena in town and the villagers beg them to investigate Fort Strat and learn what is happening. Will the heroes cleanse the town or become victims too?