Friends of ours own a former plantation house complete with former slave quarters that they run as a Bed and Breakfast in Kentucky. The former slave quarters (now known as the Annex) have been converted into two very nice bedroom units and we've stayed there many times.
During this visit, we were staying in a room located on the ground floor of the main house. There is a front door, a hallway with large, open steps leading to the second floor, a parlor on one side, a bedroom on the same side and right next to the parlor, with a living room and dining room on the other side of the front hallway. There is also a door off to the side of the main steps on the same side as the parlor and bedroom at the back of the house leading to a sun porch and a walk-way that goes out across the backyard to the Annex.
I was sitting in the living room talking with my friend one rainy April evening while my spouse and her spouse were upstairs in the office working on computers. We could hear their voices because of the open staircase. Where I was sitting, I could see the stairs, our bedroom door and the door to the sun porch. My friend was sitting with their dog on the couch across from me and could only see the front door and parlor.
A young couple had checked in earlier and were staying in the Annex, so no one else was in the main house other than the four of us. The young couple had been told to just come up to the main house if they needed ice, something from the fridge or more pillows and blankets. There are motion sensitive lights along the path from the Annex to the main house.
So, while we were chatting, the motion sensitive lights came on. You could see the light through the windows behind the steps that led upstairs (the sun porch had been added to the house after it was built). We kept chatting, waiting for the young couple to show up and I watched as the door knob on the door to the sun porch turned and the door opened.
You know how when you call someone and expect the answering machine to pick up? You kind of have a message in your mind you want to leave and then if someone actually picks up the phone it takes a second for your mind to shift?
Well, that's what happened to me.

I was waiting for the young couple to come in and so was ready to say hi and ask them what they needed. The door opened all the way to the wall and there was no one there. And the motion sensitive lights had shut off (which they never did before or after since they were set to stay on for about 10 minutes when they came on).
The door knob turned, the door opened all the way, stayed open for about five seconds and then as I watched, it shut itself completely with the door knob turning again to latch the door.
And I said: "Well okaaay then."
The dog (a min-pin who barked at everyone and everything) had her head buried in my friends lap, whimpering. My friend, who could hear the door open and shut said the look on my face was priceless, mostly because I looked rather stunned. Or as she said at the time...like someone had whacked me over the head with a board.
The sun porch door was a sticky door. It never opened easily or latched easily. I checked and there were no earthquakes in that part of Kentucky and none of us know to this day why on earth the door knob turned, the door opened, shut and the door knob turned again to latch it as there was NO ONE THERE!
We've stayed with our friends many times over the years and have never, ever had anything like this happen before or since. People have asked me if I was frightened when it happened, and to be honest, I was so sure at the time it was the young couple from the Annex coming up to the house that I didn't even think to be afraid. I can say that I could quite happily live the rest of my life never having another "experience" like that one.