Story structure
Flashforward
A scene that temporarily takes the narrative forward in time; formally prolepsis, it shows the future where foreshadowing only hints at it.
A flashforward (also spelled flash-forward, and more formally known as prolepsis) is "a scene that temporarily takes the narrative forward in time from the current point of the story." The article calls it "primarily a postmodern narrative device," named by analogy with the flashback. The near neighbor differs by showing: a flashforward "is similar to foreshadowing, in which future events are not shown but rather implicitly hinted at." Keats's "Isabella, or the Pot of Basil" (1818) proleptically anticipates a murder, A Christmas Carol (1843) shows Scrooge a future he then averts, and The Prime of Miss Jean Brodie (1961) uses prolepsis extensively; Lost and Arrival carry the device into recent screen storytelling.
The craft weight is the debt it opens: the story must still earn the future it showed, or the gap between preview and arrival becomes a broken promise. It is the foreshadowing idea run at full brightness, the mirror of the flashback, and a strong serial weapon when the pay-off is planned before the preview publishes.