Any time you label something the most important of anything you’ll get folks crawling out from behind their keyboard to argue the point. And they may be right, especially in the avocation of writing-fiction, where hard-and-fast rules about the rules are always up for grabs. It is art, after all. But I’ll stand hard and fast behind this one: The First Plot Point of your story is the most important moment in it.
We’ve spent a fair amount of time looking at this milestone already. But in the name of clarity, let’s go deeper through the use of examples.
In the film Collateral, the hero, a taxi driver, picks up a fare. At about 15 percent into the filing with all the requisite Part 1 elements in full raging glory (we’re all over the hero’s goals, his fears, and we’re already rooting for him), the passenger murders someone while the hero waits in his taxi. It’s huge — the body actually falls onto the roof of the taxi.
Seems like a new story from this point forward, right? You’d bet your printer that this is the First Plot Point. But it’s not. It’s a plot twist, an inciting incident, and a whopper.
First of all, it is a huge moment in the story, one that is very necessary to its narrative exposition. It actually could be a plot point had it appeared in the right place, but it doesn’t in this case. It’s too early. As is, it’s part of the setup for the First Plot Point. Because without it, the content of the scene that delivers the First Plot Point exposition wouldn’t make sense.
And the real reason it doesn’t function as the First Plot Point (in case someone wants to argue that it is, indeed, the First Plot Point by design, with an intentionally early placement) is that it doesn’t do the most important thing a plot point is supposed to do: define the hero’s need and quest going forward, actually commencing the dance itself.

The excerpt is retrieved from the book ‘Story Engineering’