This is more spooky than a mystery, but it is a real true life story, honest to god.
When I was 9 or 10, I went to stay with a friend of mine who lived in a big house in Durham. She was lovely but her family was a bit odd, and I found out later that her dad was an alcoholic and she said pretty violent as well.
When we drove up, me, my mum and my granny all sat in the car looking at the house. It was huge and pretty dismal looking with big stone greyhounds in the garden.
Whilst we sat in the car, honest to god, we heard something scratching down the door on the right hand side. Just as if something had walked up, put out its nails and slowly and deliberately scratched (like nails down a blackboard) down the side. Very loud and distinctive.
My mum and granny were "oh my god, what the HELL was that?!" but after seeing i was a bit scared, played it down a bit and later on said "it was probably a badger". A badger?! In broad daylight. I do NOT think so.
Now I have no idea what it was, and when we got out (very gingerly) there were NO marks on the side of the car. I spent the weekend there, and it was a spooky horrible house. It had doors that opened onto other doors with small spaces inbetween (not sure if I'm explaining it right) so you had to keep both doors open otherwise you would be locked in a tiny space. Later on my friend said that things kept being moved around, the fish kept dying and other weird stuff including stones being thrown at the windows. Bear in mind, she didn't come from a particularly happy family.
Anyway, I mentioned it to my mum the other day and she does remember it, but files it under "things that I don't really want to remember". I lost touch with my friend, and she went off the rails and the parents split up.
It was very spooky and made me feel very uncomfortable....and I never want to hear that scratching noise again...