Today's the day the teddy bears have their picnic!

Today being Labor Day, I watched Picnic (didn't you?).  You can easily roll with the Lynchian aspect of a 1950s midwestern town bursting with intrigue that explodes when a stranger appears, or you can go in a different direction.

Hal Carter is a Promethean.

It all fits.  He rolls into town, telling tall tales (he's a tabula rasa, and has pieced his history together from the sorts of things other people say).  Sure, he knows Alan, but Alan's a big name in the town.  He might have heard of the Benson family, figured out the college story, and then used his Promethean powers to convince Alan they knew each other.  The rest of the story is easily Disquiet tearing the town apart.

It's a good movie on its own (sadly, I've never seen the play, so I can't compare the two), but if you want to run a Promethean game, take a look at the progression.  Some people love Hal and some people hate him, but it's obvious that no one's life will be the same after this day.