“Another clue! And this time a swell one!”
—Joe to Frank in The Tower Treasure, the first Hardy Boys mystery by Franklin W. Dixon
Investigation is the meat and potatoes of a mystery novel. The sleuth talks to people, does research, snoops around, and makes observations. Facts emerge. Maybe an eyewitness gives an account of what he saw. A wife has unexplained bruises on her face. The brother of a victim avoids eye contact with his questioner. A will leaves a millionaire’s estate to an obscure charity. A bloody knife is found in a laundry bin. A love letter is discovered tucked into last week’s newspaper.
Some of this evidence will turn out to be clues that eventually identify ...