What happened here was that this writer likes to work out his plot structure as he writes his draft and doesn't want to create the framework for his plot before plunging into the actual script. As a result, what inevitably happens time and again is that everything--all those many, many first draft pages--have to be put aside and the structure of the story has to be developed and planned out from the ground up.
It's like building a three story building and realizing when you get up to building the third floor that the load has become so great that this final floor can't be supported by what you've built underneath--the foundation and first and second floor can't hold the third.
It might look something like this underneath the surface...
So everything has to be dismantled stick by stick (or scene by scene, page by page) until you're back to square one and you're looking at your original hole in the ground. And you have no choice--painful as it may be--but to figure out and create viable working drawings before you can attempt reconstructing your edifice.
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I'm the Program Director of the low-residency MFA in Writing for Stage and Screen being offered by the New Hampshire Institute of Art. Our last residency ran January 3-11, 2016 and we are now considering applications for starting the program with our July 2016 residency that runs July 21-31. I'm also a playwright and screenwriter, producing partner in my production company Either/Or Films (The Sensation of Sight and Only Daughter), a professional script consultant, and the author of The Playwrights Process.