Drawing from a book...

A village is found, relatively prosperous for the setting. Like, not rich, but people have enough food and water to survive, and decent-enough clothes and shelter. It's an eclectic mix, and they welcome the PCs, being friendly. They offer room and board for the night--not insistent, but offering and feeling sad if hospitality is rejected.
A little after night falls, every villager goes into a bloodthirsty rampage and they slaughter each other, and the PCs if they can, and wrecking the town.
In the morning, with the break of dawn, the village "reshapes" back to an undamaged, unblood-stained version of itself. Effectively time-shifting back 1 day. Except everyone who died is back, and any visitors who died are now villagers who have been there 'as long as anyone can remember'. A PC (or NPC ally who was with them) who dies is glad to see his old friends and hopes they will stay the night, but refuses to leave the village now that it's become home.

Though, honestly, not a great plothook for a D&D-esque campaign and, if a PC dies, it effectively becomes an NPC...
(If someone is forcibly removed, they still go into a bloody rampage at night and time-shift back to the village the next daybreak.)