Help me build out a horror session(s)
So I have an idea for a slow discovery horror comedy concept for my party if 4 lvl 3 players of a small secluded town/community they meet on the road and am seeking tips, advice, fleshing out of what I think can be a multi session folk horror 'Adventure' for my party.
The idea: The party (lvl 3 Dwarf Forge Cleric, Haragon Lore Bard, legacy Half Elf homebrew Warlock and Tiefling BM Ranger) arrive in a small town hoping to find a long rest to find a seemingly normal town until they eventually notice that the town is overwhelming populated by older people (species realitive 60s+), they're are younger people but vastly outnumbered and only serve functional/service roles in the town (an overly nervous tavern server, a quiet shopkeep so)
The Eventual Reveal: The town is known to be a retirement community where older folks live out their later years in peace but a Demon (I'm thinking a Bulezau) has dealt with the old folks in their retirement community to give them youthful vigor and supernatural strength (buffed Strength and Constitution above that from the normal Commoner stats, maybe even the occasional Berserker stats, but a town off multiple would be potentially deadly) and now outnumber the youthful inhabitants of the town and are forced to remain indoors during the day so that the supernaturally imbued old folks of the town has completely taken over and relive their youth whilst believing their younger town folk to be naive and need to be protected from the outside world from their towns boarders.
Mainly wanting tips, advice and a sounding board for idea as to what to add to prolong the mystery, instill terror and uncertainty and beef up an idea I currently have and see if I can beef it up because I think it'll be fun.