There could be many reasons for that. Check and make sure that there is no logical explanation first before you put the blame on ghosts. However if you've already done this and found no logical explanation for it then it is possible that it is in fact the dead trying to communicate to you. I would not suggest you try to communicate back to it though. I would be most unwise. Take it from a person who has had experience with ghosts. After I tried to communicate with ghosts once and wound up getting hurt because of it. Both physically and emotionally. Trust me, do not try to communicate with it if you do not know what kind of a spirit or ghost it is.
It could mean they are vandals.
On the door knocker of the front door
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That there is a burglar in residence looking for work.
Ghost Stories - 1997 I At Death's Door 1-26 was released on: USA: 16 February 1998
He makes a sign on Bilbo's door that the dwarves interpret to mean "burglar for hire", which brings them into Bilbo's house.
Durin' the halloween party you need to enter the ghost mansion. Then go through the door on the right ( -> ). Then go through the door at the top of the room. Then go through the door on the left (
In a civil peace story, thieves knock on the door in the middle of the night.
Once you cat is in for the night, block the cat door.
I think the ghost next door
Go into the basement door and you will be in.
Follow the cherry blossom petal or flower petal that make you to secret door.