Inciting incident

The inciting incident (or catalyst) is "a dynamic event" late in the setup that "confronts the main character" and upends the ordinary world; the protagonist's first response is to "attempt to reestablish order." In three-act structure it drives the story toward the first plot point, the threshold that "ensures that life will never be the same again for the protagonist," and it raises the dramatic question the rest of the book answers.

Its craft weight is proportion: everything before it is setup and everything after is consequence, so a late or weak inciting incident is the classic opening-chapter failure. Web fiction compresses it hard, sometimes into the first paragraph, as Truck-kun jokes about. It hands off directly to the rising action.