J.J. Abrams says his unopened mystery box from childhood represents “infinite possibility,” the sense of potential that hangs in balance with the unseen.
Grab your notebook! Trap your characters inside of a mystery box–a car, a freight container on a moving train, a basement, a kleenex box on a desk–any space, at any scale. Describe the setting and tension as accurately as possible without ever finally revealing exactly where they are.
Not feeling it? Revisit a piece of your writing and think about the unseen or off-screen details that haven’t been exploited. Exploit them.