I was in the basement of my Grandma's house, and I was with someone that was helping me learn the tricks of being a ghost. Some other family actually lived in the house now... I think it was Tom Cruise, actually.. but the whole focus of this dream was learning to get around the house, using my ghosts skillz, but without being detected by the family that lived there.
My helper gave me a sheet of paper. This paper was required if I wanted to travel through doors and walls. I'd hold the paper, a glow would cover me, and then I could pass through solid objects without any resistance. However, I was told that I couldn't just go barging through walls at any speed that I wanted.
In order to remain unseen, ghosts have to creep through solid objects. If we tried to go through them too fast, the living would be able to detect us. I did it the right way a couple of times, to see if I could do it... and then of course I had to try to go through something fast to see what would happen.
I went through the brick wall separating the living area from the laundry area at a quick pace, and when I did I could tell that the glow around me was also visible to the people doing their laundry. Since my presence had already been detected, I backed through the wall and did it again - even faster this time.
I must have been VERY visible this time, because I rushed up to a little girl that was standing there - and whatever it was that she saw in me, it scared her so much that her face deformed. Her eyes sunk in and turned black, her skin became pale, and her face took on that look that you saw in the movie The Ring, when people are killed by the girl in the tape. :-) I win.
