There's a principle in physics called the inverse square law. You'll have encountered it in school: the intensity of light, or gravity, or sound, diminishes in proportion to the square of the distance from its source. Double the distance, the effect doesn't halve – it quarters. It's a ruthless relationship. This week off the water I've been thinking lately about whether something similar operates in what you might call the information economy of a thriller or a mystery. Not as a precise...