A reversal is not a surprise. A surprise is new information; a reversal is a change of position using information already in play, which is why good reversals feel inevitable in retrospect and cheap ones feel like the writer changed their mind. The difference is whether the elements were on the table beforehand.
Reversals are the main defence against the flat middle. A sequence of escalating obstacles is monotonous no matter how large the obstacles get; a sequence in which the protagonist’s position inverts twice has a shape. Two well-placed reversals are worth more than five additional complications.
At scene level, the test is whether the person with the power at the start of the scene still has it at the end. If they do, and nothing else changed, the scene is probably doing one job that could be done in a line.
What is a reversal in a story?
A moment where the situation inverts — the advantage becomes the liability, the victory becomes the cost. It works with elements already established rather than with new information.
What is the difference between a reversal and a twist?
A twist adds information the audience did not have. A reversal re-orders what they already knew. Twists can feel arbitrary; well-built reversals feel inevitable afterwards.