Red herring:
a piece of information or suggestion introduced to draw attention away from the real facts of a situation. (A red herring is a type of strong-smelling smoked fish that was once drawn across the trail of a scent to mislead hunting dogs and put them off the scent.) The detectives were following a red herring, but they’re on the right track now. The mystery novel has a couple of red herrings that keep readers off guard.
