The First Pinch Point in a Story

The antagonist character will almost certainly make an appearance by proxy. At this point in the story, he will have become aware of the protagonist in some capacity. The first pinch point should be a significant reminder to the protagonist of the antagonist's ability to prevent her from reaching her goals. Their encounter with each other at this point creates consequence and their attempts to grapple with those consequences will engineer the entirety of the plot conflict.