A Strange Possession

So last night I had a pretty scary dream. I was at someone's house and there was a party or some kind of family gathering going on. All my aunts and uncles and cousins were there and my parents and there friends too. I think it must've been late because I left and walked home, which in this case was right across the street. When I got there my sister and her boyfriend were talking and she wanted me to go with her back to the house because it was haunted. She wanted me to help her get rid of the demon. So I followed her back outside and as we were walking up the steps of the house she let out this animalistic scream and passed out on the ground. My grandpa came rushing over to help. I was holding her up and she had this huge boil on her head. My grandpa had a glass filled with water upside on a plate and he placed the plate on my sister's head and proceeded to tap the bottom of the glass three times. While I was holding my sister she was thrashing around in my arms and it became obvious to me that she was possessed. I closed my eyes and imagined this cloud being pushed out of her. After awhile she layed still and the demon was gone and so was the boil. My grandfather had trapped the demon in the glass of water. I now remember I saw that on the history channel while I watching A Haunting.