A plot twist is an unexpected turn that changes what the reader thought was happening, usually by revealing a hidden fact or reversing a situation.
Where the term comes from
Merriam-Webster includes among the senses of twist an unexpected turn or development. The idea is old. Britannica describes peripeteia as the turning point in a drama after which the plot moves steadily to its resolution. Aristotle discusses it in the Poetics as a shift in the fortune of the tragic hero from good to bad, and it is often ironic: in Sophocles' Oedipus Rex a messenger brings news that Oedipus expects to cheer him, and the news instead begins the recognition that ends in catastrophe. The Wikipedia article on plot twists describes the modern device as a radical change in the direction of the plot, notes that one near the end is called a twist ending, and says a twist may be foreshadowed even though it usually carries some surprise. It lists methods such as withholding information and misleading with ambiguous or false information.
An example
Everyone in the dairy believes the missing deed was stolen by the apprentice, Joaquim. The reader sees him sweat, stammer and avoid the owner's eyes. The twist comes when the owner, Bettina, admits she hid the deed herself so the dairy could not be sold, and that Joaquim has been protecting her. The clues were there from the start: Bettina always wore gloves in the cellar, she was the only one who never joined the search, and Joaquim's nervousness began each time she entered the room. On a second reading, every scene means something else.
Common mistakes
- A twist with no preparation. If no earlier line supports it, it feels like an author's convenience, which is the territory of deus ex machina.
- A twist that cancels earlier emotion, such as revealing that events were a dream, so the reader's investment seems wasted.
- Hiding the clue so well that nobody could find it, or showing it so loudly that everyone can.
- Surprise for its own sake. A twist is stronger when it changes what the story means or what a character must now do.
How to check your manuscript
Write the twist in one sentence. Then read from the start and mark every earlier line that supports it. Each marked line should read innocently the first time and meaningfully the second. If you find none, add them; if you find many that all point to the same place, make some of them quieter or give a rival explanation, the way a red herring does. Then test the reveal itself: what does the main character do differently after it? A twist that changes nothing is easy to forget. The foreshadowing entry shows how to plant the clues.
In Musael, continuity checks can show which scene first taught the reader a fact, which helps you confirm the clue is on the page before the reveal.