"McGuffin" is a Hollywood term for an item which a majority of the plot centers around the characters trying to find and/or protect, but which has minor significance to the plot itself (the Holy Grail in Indiana Jones and the Last Crusade (1989)). Hence, the money and the body which are found and lost at the beginning of this film, are the title's "Double McGuffin".
A "McGuffin" is a term coined by the world's foremost teller of suspense stories to label that secret, elusive, mysterious something that everyone in the story is trying to find or find out about. It is, in effect, the pretext of the plot; the ...
When Specks circles the name 'Crabtree' in the racing form, the camera and two crew members are seen clearly reflected in a mirror.