In the desolate wastes of Antarctica, under thick layers of ice and snow, forgotten by the world and only remembered in a few databases of the ancients: There lies Psilabs; a major research complex into the human psyche and the powers of the human mind.
In the ramshackle town of Spear Malice only a single building still stands. It has defied the Great War and its spears of light; nuclear blasts that devastated the entire state, and ever since then it has defied the onslaught of time.
Its halls have not yet been breached, and a wealth of technological treasure await, ripe for plunder! But there are others who crave this treasure; others that will do anything to claim it.
In the dark alleys of Malcaresh, the Caravan City of the Plains, many an adventurer meets his death at the end of an unseen blade. Even more part unwillingly with their belongings, having fallen victim to the thieves and cutthroats plying their old and ignoble trade. Yet even among these, the whispers of House Caraguil invoke fear and discomfort.
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?