Exactly when was that?
Part one gave you one reason why and when an audience leaves the theater.
An important aspect of relating a screen story is something called “willing suspension of disbelief.”
That is, how easy is it for your audience to suspend disbelief and go along with the story/plot, as well as what your characters do and say?
When watching a movie, audience members must suspend their critical faculties, must be willingly to sacrifice realism and logic for the sake of enjoyment. This is true for most any story.
But that willingness of theirs only goes so far.
If the writer has not efficiently, and effectively, and believably set up the rules of the universe of the story, or if the writer uses too heavy a hand in crafting a character or sequence of events, or if the writer creates story elements that are too distracting or fantastical, or constructs an event that is too much of a challenge to one’s emotional or mental faculties, his audience’s suspension of disbelief is violated.
That delicate bubble he has heretofore successfully crafted has burst.
The very second that happens you have totally and completely lost your audience.
This is as true for the Reader your screenplay will encounter when submitted for production consideration, as it is for watching audiences.
As a writer you never want to hear, “Oh, give me a break!” or “You’ve got to be kidding me!” or a similar sentiment.
The moment you do, it’s a sure sign, like Elvis, that your audience has left the building.