How Jayel became the proprietor of the Wanton Wench is more or less a hand-waved affair by the local officials. The facts known by 'upstanding' folk are that a fresh-faced young girl by the name of Jayel came into Gatewatch, disappeared, and reappeared the aged and stern woman she is today. The facts known by the night watch are a marked decrease in drug trafficking and battered women appearing on the streets. The fact known by Jayel is that she killed a man with her bare hands, and has never looked back.
A vicious murder happens in a town that the party happens to pop in at. Under heavy suspicion as they are strangers, the party is forced to discover the perpetrator or have their reputations blackened, especially as more and more murders occur in the town, and mysteriously stop and restart when the party leaves to go kill off that evil necromancer who kidnapped the princess.
The only problem is that a demon, possessing one of the party, is the perpetrator. And the demon makes no signs that its living in the PC's head.
In fact, for all the party knows (except for the possessed person's), their companion is an evil murderer.
Do they try and execute their friend as he's a vicious murderer, and no evidence points to demonic posession? Or do they flee town with him, trusting him, and have their reputations destroyed?