Killer Instinct (2001)

A group of teenagers go to an abandoned insane asylum, which turns out to be incredibly clean and full of hundreds of lit candles.  The friends have a club, either called the Fear Club or the Dare Club, I'm not sure which as what they do is neither scary nor daring.  The task tonight is a scavenger hunt where they must each hide someones underwear and whoever finds the most undies is the winner.  Ridiculous for so many reasons, but most importantly this place is three stories high and huge. How would they ever find even one piece of underwear in it?

Meanwhile Sarah Fairchild, played by Dee Wallace, is in town to make an offer on the meat packing plant, which is the life blood of the town.  But when the board angrily refuses to sell,  this causes Fairchild to snap into hard boiled detective mode as she delves deeper into the small town's history.  She scours microfiche and libraries in a frenzy to find out what is so important about the land and the asylum, and finds a scandal that has been buried and untalked about for years.

Back at the asylum, the kids have gotten locked in and things are starting to go horribly wrong.  There's a killer locked in with them, but they don't realize it.  So they do the normal things that teens do when they go to an abandoned asylum - wander off on their own, have sex, and take a shower.  There is no explanation for why the shower is clean and working, why the bed sheets are not dusty or dirty, or for the lack of any filth anywhere in the abandoned building - which if you didn't set up the scenario that it had been empty for years, you'd think someone lived there.