Foreshadowing

Foreshadowing is "a narrative device in which suggestions or warnings about events to come are dropped or planted." The hints can travel through "character dialogues, plot events, and changes in setting"; even a title or chapter heading can serve as a clue. Usually planted early, it shapes what the audience expects, builds anticipation and dramatic tension, and makes the later event feel credible rather than arbitrary, because the reader half anticipated it.

The craft distinction is intent: foreshadowing points at what will truly happen, while the red herring misleads deliberately. It is also the mechanism behind Chekhov's gun: the rifle on the wall is a planted promise. Web-serial writers carry a special risk, because a clue published in chapter one cannot be quietly removed two hundred chapters later.