This element of surprise or mystery - the detective element as it is sometimes rather emptily called - is of great importance in a plot. It occurs through a suspension of the time-sequence; a mystery is a pocket in time, and it occurs crudely, as in "Why did the queen die?" and more subtly in half-explained gestures and words, the true meaning of which only dawns pages ahead. Mystery is essential to plot, and cannot be appreciated without intelligence. ... To appreciate a mystery, part of the mind must be left behind, brooding, while the other part goes marching on.