The wrong letter

"The fine detective story, be it repeated, does not consist of a clue. It is a ladder of clues, a pattern of evidence, joined together with such cunning that even the experienced reader may be deceived: until, in the blaze of the surprise ending, he suddenly sees the whole design."

- John Dickson Carr ("The Grandest Game in the World," 1963)

"Gold comes in many forms. For literal-minded people gold may be merely a precious metal, physically stripped from the earth. For fans of Golden Age detective fiction, however, gold can be artfully spun out of the human brain, in the form not of bricks but books."