Then there are the so-called extraordinary activities of the devil in the world. Usually these are material things around a person that are affected; taht might be what you’re up against. We call it infestation. It breaks down into different categories which we’ll explain in a minute. Obsession is the next step in which the person is affected either internally or externally. And finally there is possession, by which the person temporarily loses control of his faculties and the devil acts in and through him.
|—||Jay Anson, The Amityville Horror|