A deliberately misleading clue that steers suspicion the wrong way - a staple of mystery and suspense.
A red herring is a plant designed to mislead: a suspect with a motive who didn't do it, an object that looks like the key and isn't. In mysteries it keeps the reader guessing by making a false lead as plausible as the true one, so the real solution hides in plain sight.
The line to walk is fairness. A red herring should be explainable in hindsight, not a cheat - the reader who feels tricked rather than outwitted stops trusting the game. Contrast it with foreshadowing, which hides a true signal rather than a false one.
Go deeper: How to Write a Mystery Novel
Plan with 30+ story frameworks, write your screenplay or novel, and let Quill coach every beat - it guides and never writes. Free account, no card.