The notion of ghosts and spiritual phenomena is something that has captivated mankind since the beginning of history. This ghostly documentary dives deeper into the scientific aspect of ghostly phenomena. Ghost, nonmaterial embodiment or essence of an organism, especially of a human being. The term is sometimes used virtually as a synonym for soul or spirit, and in the Christian religion, in the form Holy Ghost (now, more often, Holy Spirit), it has a specialized meaning. More frequently, however, the term ghost is applied to an apparition, usually of a dead person, that varies in apparent solidity from a mere foglike mass to a perfect replica of the person. A wraith, in contrast, is the visible spirit of someone still alive. A doppelgänger is a special form of wraith that makes its appearance at a time when the physical body of the subject is observed at some distant place.