Big Mearle, that's too Kooky!!!!
I talked to DH today...
One of his suggestions:
They have a bet going....They want to see how many white paper bags can fit into a room. Well, now there's sooooo many white paper bags in the room that they can't even get the bedroom door open, so they have to throw them in the window
Maybe you can be like Mission:Impossible and go through the neighbor's trash early early in the morning on garbage day and look for the used white paper bags?
When you're sure everyone is out of the house (like on Flea Market Weekends), just get your nerve up and walk up to the window and take a peek inside?
Check to see if there is a lock on the window and where the lock is positioned: On the inside of the house like normal people or if there's a latch on the Outside of the window.
I know you mentioned that there are blinds, but don't the blinds have the tiny little holes where the rope goes through? Listen, if Peeping Toms can see through them, then maybe you can too!
Personally, I think there's someone holed up in that room, be it Gramma or Grampa, kidnapped person, severly violent mental person, somebody.
At least once a year we hear a story on the news of some child who was holed up in a closet, under a bed, in a basement for years and years and years.
I would try to document it - if it's innocent in the end, you're just a nosey neighbor like the rest of us. Technically it's called Neighborhood Watch, right? But if something hokey is going on, you'll be the gem of the neighborhood.
In any case, keep us informed when your fingers can handle it
This friend of my mothers who lives up the street from us was coming home for lunch on Friday. She said as she drove onto the cul-de-sac there was some woman in our yard. She said she had some plastic grocery bags full of greenary and looked like she was cutting on our Azalea bushes. 
