Story structure
Red herring
A false clue planted to lead readers toward a mistaken conclusion; the mystery writer's tool of deliberate misdirection.
In fiction a red herring is "a false clue intended to lead readers or audiences toward a mistaken conclusion." The phrase comes from the strongly cured, reddish kipper; its figurative use was popularized by William Cobbett's 1807 tale of dragging one over a trail to throw hounds off a scent, though etymologists have shown that story itself spread a false idea about real hunting practice. The same name covers the relevance fallacy in argument, a diversionary tactic that is not necessarily intentional.
In mystery fiction it is a load-bearing device. Holmes's "Rache" clue in A Study in Scarlet points police and readers at the wrong suspect; Aringarosa in The Da Vinci Code is a red herring by name, a loose Italian play on aringa rosa. For the writer, the honest red herring misleads with true facts, which is what the fair play mystery contract demands, and it is the deliberate cousin of Chekhov's gun: a gun hung on the wall that the author means never to fire.