twist, peripety, peripeteia
the inversion from one state of affairs to its opposite. For example, an action seems destined for success but suddenly moves toward failure, or vice versa. According to Aristotle, peripety is, along with recognition, the most potent means of ensuring the tragic effect. (Prince, 1987), a sudden reversal of a character's circumstances and fortunes. (Baldick, 2001, p. 189) [As a plot point a] twist is surprising, yet explainable and motivated change in the direction of the action. (International Screenwriters' Association, 2017); in a "tragedy" usually involving the downfall of the "protagonist", and often coinciding with the "recognition" or "anagnorisis"; in a "comedy", however, the [twist or] peripeteia abruptly restores the prosperity of the main character(s). (Baldick, 2001, p. 189) Also see coup de theatre, hamartia, anagnorisis