PERIPETIA, a literary term
Aristotle defines it as "a change by which the action veers round to its opposite …." According to Aristotle, peripeteia, along with anagnorisis, or discovery, is most effective when it comes to drama, particularly tragedy.
Aristotle considered anagnorisis leading to peripeteia, the mark of a superior tragedy, tragedy being defined as a theatrical imitation exciting fear and/or pity. The effect is often an ironic twist, as in Oedipus Rex, where the messenger brings Oedipus news about his parents, expecting it to cheer him, when, instead, it brings the awful recognition kills his mother and blinds and exiles him.
The most stunning modern example of this I know is the reversal of interpretation occurring between two "first contact" SF novels by Mary Doria Russell; While clerical types refer to these books as "Jesuits in Space," they are properly titled THE SPARROW and CHILDREN OF GOD.
Where I find I can apply the word, however, is not to tragedy, but to the turn in a mystery novel wherein the reader realizes that all the clues that appeared to point to the butler are correctly interpreted to reveal the murderer as the scullery maid.
----- Linn Prentis