the term "ghost" can have many different definitions. That being said, I do not believe in spirits of dead people influencing the living for good or ill, or have the ability to make their presence manifest. However I do believe that demons can effect people, make them see & experience things etc... only if they open themselves up to it.
This is more a mystery than an experience however... Shortly after my wife & I got married I purchased the Lord of the Rings trilogy on audio book CD in anticipation of the films coming out. I would listen to them as I would fall asleep at night. One time I woke up in the middle of the night and my arm accidentally knocked the CD's off my nightstand. Four of the 12 CD's for Return of the King were missing, and I never found them. Tore the bedroom apart. Even when we moved out of that place I never found them. There is a small chance one of our neighbors teenage daughters, who has he reputation of stealing things,
may have done it, but I cold have sworn ALL the CD's were there the night before I knocked them off the nightstand.
There are no more good TV Shows, only ones that haven't disappointed me yet.