I once wrote a spec script in which one character had psychic powers, but I was a little sloppy about the rules. The powers worked slightly differently from scene to scene, depending on what sort of danger I wanted to create. My managers loved the script but insisted that I nail down exactly how the powers worked in the next draft. I thought this was silly. The audience doesn’t care about a bunch of rules, I thought, and the powers are just a metaphor anyway. Why not bend the rules as I go along?
It took me years to figure out why I was wrong. The rules of your world have to be perfectly clear so that your audience can try to anticipate what might happen next. Audiences engage with movies by playing a guessing game. “How will the hero solve the problem? What would I do in this situation? Will I spot the heroes’ solution before they do? Or will they come up with something I didn’t spot?” But the audience can’t play that game if they don’t know all the rules.
That is why we need to know the exact powers of your superhero, and exactly how physics works on your fantasy world, and exactly what the threats are facing the family farm in your drama. The heroic finale, the surprising twist, the solution to the mystery all need to be things that the audience could have anticipated, or they will be unsatisfied.
If you’ve created a world where anything can happen, you’ve messed up. You should create a world in which one of five things might happen, and the reader can’t decide which of those five it will be, and then they’re shocked which one happens. Or maybe a sixth thing happens that they didn’t suspect, but they instantly realize that they should have considered that possibility.
Although few moviegoers guessed what was really going on in the remake of Ocean’s Eleven, it still felt fair when all was revealed. We realized that we really had seen enough to guess, and now we were kicking ourselves for failing to pick up on the important clues.
People walked out of that movie feeling dazzled, so of course they made a sequel, but in the sequel, the moviemakers just cheated. In the final twist, they revealed that the gang had secretly achieved their goal offscreen, and everything after that was just an elaborate con. Audiences were viscerally disgusted. They had been tricked into playing a rigged game, one that they had no chance to winning.
The audience is your opponent on the other side of the chessboard, trying to figure out what you’ll do two moves ahead. Even if you win that game, they’ll be happy to get a pleasant mental workout. But if you just cheat and change the rules halfway through, they’ll never want to play with you again.