Hitchcock's 'Maguffin'

A Maguffin is a plot device that motivates the characters and advances the story, but has little or no relevence to the story.
Alfred Hitchcock Quote "we have a name in the studio, and we call it the maguffin. It is a mechanical element that usually crops up in a story.In crook stories its always the necklace and in spy stories its always the papers"
An example of a maguffin is in 'Notorious'