MacGuffin
The target object everyone is chasing but which is almost unimportant in itself (the briefcase, the document, the formula) — it moves the film, the meaning accumulates in the characters.
Distinction: A MacGuffin is a GOAL object, not a plant & payoff: a plant & payoff pays off its counterpart at the end, a MacGuffin doesn't — its job is already done along the way.
Common mistake
Mistaking the MacGuffin for the film's meaning: the audience doesn't watch the briefcase, it watches what's done for the briefcase's sake.
Example
Think of an envelope. What's inside is never said in the film. Three parties are after it: one for a career, one for a brother, one for a debt. Every time the envelope changes hands all three are forced to do something, and what they do says who they are. In the finale the envelope burns — and the film loses nothing, because the envelope was the carrier, not the load.
How to use it
- Write out separately why each of them wants it. What makes a MacGuffin valuable isn't the thing itself but the fact that the costs paid for it differ from one another.
- Don't feel obliged to explain what's inside. If you explain it, the argument slides onto the object itself; if it stays closed, it stays in the characters.
- Make them lose it. The moment the thing being chased is caught, the film ends; if you want it to go on, the object has to change hands.
- Don't tie the finale to the object. The audience isn't watching the briefcase, it's watching what's done for its sake.
Check
Put a completely different object in the MacGuffin's place — a key, a tape, a list of names. If the story stays the same, it's built right; if it collapses, what you have isn't a MacGuffin but the film's actual subject.