We moved into the house where we live now back in October. The place had a very strange, creepy vibe to it. I didn't put much into it, as the house is very old, but my wife wasn't able to put it out of her mind as easily. She claimed she heard footsteps on the stairs at night, sounds in the attic.
Anyway, fast forward a week, I come home to the front door open. Now, we live in a good neighborhood, so although I was concerned, I wasn't too worried. I go through the house, carefully, room by room, making sure nothing was taken and that no one was around. I get up stairs, go through the rooms one at a time; bathroom, my office, master bedroom, guest bedroom... when suddenly I hear what sounds like someone running down the stairs behind me.
I bolt down the stairs, hell bound on catching whoever I just heard...
And no one is around. I go through the house two more times, and it's completely normal.
My wife's best friend is one of those super spiritual types, like a modern hippy. She comes over that weekend and they burn sage throughout the entire place. They do the first floor, the second floor, and then go into the attic.
They both swear that when they opened the door to the attic they heard someone run up the stairs and stumble into one of the back corners. But they don't stop and finish saging the place.
Haven't had any issues since then... except our cat won't stop sitting by the front door now, as though he's expecting someone to come home...