I think I might have broken one (or more) of my players' brains tonight...
The adventurers emerged from the magical portal not to find themselves in another world or plane of existence but to find themselves transported near the top of one of the mountains that overlooked the city.
As they ascended the mountain they were attacked by an old adversary, worse still and adversary they had already killed in the previous session. Somehow the halfling cult-leader they had killed in the Hall-House was alive and well on the mountainside.
In addition he had some magical snow-globes that when hurled unleashed Ice Imps upon the party.
At the top of the mountain the party discovered a secret lab being attended to by Philos The Red, the NPC who's alleged death had kicked off the whole adventure in the first place.
During an encounter with Philos and his Sentinel an equipment malfunction resulted in Philos' untimely (well-timed?) death.
The party started back towards Thatchertown in some boats they discovered in a grotto behind Philos' lab but they decided to stop along the way back at the Hall-House to recover some materials they had left behind. When they got there the house showed no signs they had ever been there, nor had any of the damage to the property or monster habitation ever occurred. They returned up the mountain and discovered there was no sign of a lab either.
What is going on? What will our heroes do next?