The Maguffin.

The MaGuffin has been described as a plot device, or a gimmick. It is a technique used in a film to create the story of the film. The MaGuffin of a film does not really matter and the viewer does not really care about the MaGuffin in a film, but this is used as something that gets the film started. The MaGuffin was made popular by the great Alfred Hitchcock, who used a MaGuffins in many of his thriller films.

A Macguffin can play as a wild card in a film that is unexpected to the viewer as it progresses over the film. It is something that can also be irrelevant to the viewer but is used in the film to carry along and aid the reason for decisions made in the film.  The MaGuffin has been used in some of Hitchcock's most successful films e.g. North by NorthWest and Psycho.