peripetia
/ˌpɛrəpɪˈtaɪə/
noun
- A sudden and unexpected change in a situation, especially in a story or play, that reverses the main character's fortunes.
- The hero's sudden loss of his kingdom was a dramatic peripetia that shocked the audience.
- The movie's peripetia turned the happy ending into a tragedy in just one scene.
- In the novel, the peripetia occurs when the detective realizes the butler is the real criminal.