The adventurer rode into the golden-hued glade, looking around. If the tribesman he had 'persuaded' to help him hadn't been lying, it should be here. Ah, there it is, he thought. A small pool, with no inlet or outlet. Dismounting, he looked into the crystal-clear water. He could see goldfish swimming around, and beneath them the bottom was covered with golden statues of men and women, mostly nude but some with a kilt or loincloth.
“I'm rich,” he exulted. “That damn tribesman didn't die in vain!” He stripped off his clothes and armor, noting in passing that the ground was mounded, here and there, with weapons, armor, and other items, mostly rusted or rotted by time, and dove into the pool to begin gathering up his wealth.
Silence fell over the glade as the new statue settled onto the others littering the bottom.
"Hey, Hultz. What are you doing in here?"
"It's gonna move. I don't like it when it moves," the stableboy replied, sitting by the hearth with his arms wrapped around himself.
"What's going to move?"
"The Inn. I don't like it when it moves."
Five minutes later, he gets up and goes back outside.
"What was he talking about?" the newcomer asked a burly fighter.
"Go outside and take a look."
He goes over to the door and flings it wide. "See, it's all still ... Wait! Where did the town go!"
"Welcome to the Brotherhood of the Wild Geese." The fighter comes over with a mug of ale. "Here, you'll probably be needing this. I know I did, when it happened to me."
The secret for immortality has been discovered by an eccentric wizard/mad scientist. Its found you need to reapply once a month. As people stop dying, and the birth rate increases exponentially, people are forced into homelessness, because of the need for food reamins the same, and food is not being produced fast enough to feed the undying population. The PCs have to find the creator and kill him, and destroy production, to save the world from undying, unending torture from hungryness.