In the story, “The Adventure of Silver Blaze”, Sherlock Holmes solves a mystery in part by when no one he’d spoken to during an investigation mentioned that they heard a dog bark the night a famous race horse was stolen and the horse trainer was killed in a stable. See the exchange below: Scotland Yard Detective to Holmes: “Is there any other point to which you would wish to draw my attention?” Sherlock Holmes: To the curious incident of the dog in the night-time.” Scotland Yard Detective: “The dog did nothing in the night-time.” Sherlock Holmes: “That was the curious incident!” The fact the dog didn’t bark led ... (full story)