Ben-Affleck-in-Gone-GirlIf you think you know how David Fincher’s Gone Girl is going to end, think again.

Following yesterday’s new preview of the anticipated adaptation, news now surfaces that Gillian Flynn, author of the original book and writer of the screenplay, has a whole new third act in store for us when the film hits screens later this year.

In the latest print issue of EW, via The Film Stage, Flynn says,

“Ben [Affleck] was so shocked by it. He would say, ‘This is a whole new third act! She literally threw that third act out and started from scratch.’”

The author/screenwriter also goes into detail a little on wanting Fincher to direct the film from the get-go, and believing Affleck to be perfect for the role of Nick.

“When I was writing Gone Girl there were certain parts where I thought, ‘David Fincher would really kill this scene,’” Flynn says. “I thought he’d inject just the right sense of necessary malice.”

“Ben knows inherently what that experience is like. He knows what it’s like to be hunted. You have to wonder if Nick did horrible things to his wife, and you have to see him do some really not good things, but at the same time you have to able to say, ‘I’d like to have a beer with that guy.’”

Courtesy of Amazon, here’s the original novel’s synopsis.

Marriage can be a real killer.

One of the most critically acclaimed suspense writers of our time, New York Times bestseller Gillian Flynn takes that statement to its darkest place in this unputdownable masterpiece about a marriage gone terribly, terribly wrong. The Chicago Tribune proclaimed that her work “draws you in and keeps you reading with the force of a pure but nasty addiction.” Gone Girl’s toxic mix of sharp-edged wit and deliciously chilling prose creates a nerve-fraying thriller that confounds you at every turn.

On a warm summer morning in North Carthage, Missouri, it is Nick and Amy Dunne’s fifth wedding anniversary. Presents are being wrapped and reservations are being made when Nick’s clever and beautiful wife disappears from their rented McMansion on the Mississippi River. Husband-of-the-Year Nick isn’t doing himself any favors with cringe-worthy daydreams about the slope and shape of his wife’s head, but passages from Amy’s diary reveal the alpha-girl perfectionist could have put anyone dangerously on edge. Under mounting pressure from the police and the media—as well as Amy’s fiercely doting parents—the town golden boy parades an endless series of lies, deceits, and inappropriate behavior. Nick is oddly evasive, and he’s definitely bitter—but is he really a killer?

As the cops close in, every couple in town is soon wondering how well they know the one that they love. With his twin sister, Margo, at his side, Nick stands by his innocence. Trouble is, if Nick didn’t do it, where is that beautiful wife? And what was in that silvery gift box hidden in the back of her bedroom closet?

Affleck stars opposite Rosamund Pike as his on-screen wife of five years, with Missi Pyle, Tyler Perry, Scoot McNairy, Neil Patrick Harris, Kim Dickens, Patrick Fugit, and Casey Wilson completing the ensemble.

Without a doubt, there will be much debate when the film is released about the third act and how it differs from the book. As ever, there will be some who think it criminal that it was changed for the film, but hopefully more will be the voice of reason. At the very least, given that it is Flynn herself who has penned the script and changed the ending, you can have a little faith that it’s going to have a brilliant final act. Whatever your thoughts, it’s nice to know that the only people who know how it’s going to end are the ones who made the film, which isn’t something you can normally say about an adaptation like this.

Gone Girl will be released in the UK and US on October 3rd, a date that could well see it become a prime contender for Fox in the height of the awards season this time next year.