Maybe, so you have an idea with sets, you could have the entrance be a graveyard and the building be a mortuary, just so you can have something in mind whne building. I kind of don't think this will need a story (because of time) but if there was one, the "caretaker" ran the mortuary, until his death in 1894 (I don't know if where you live will fit the time period but it can easily be changed) He was hit by a van of gypsies as he was leaving one day(I don't know if that is the plural of gypsy but whatever, also i don't mean a modern day van, but a horse drawn one of course) and as an apology they brought him back to life, but the spell of the gypsy only works on halloween (or when ever you do this) also their power was so strong they brought to life the whole grave yard.