Gillian Flynn has revealed that the third act of Gone Girl is completely different to the book.
Gone Girl sees David Fincher return to the director's chair for the big screen adaptation of Flynn's novel.
Flynn herself has adapted her book into a screenplay, and admits that she enjoyed the process of re-writing her own work.
Speaking to Entertainment Weekly, the author said: "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'."
"There was something thrilling about taking this piece of work that I'd spent about two years painstakingly putting together with all its 8,000,000 LEGO pieces and take a hammer to it and bash it apart and reassemble it into a movie."
Ben Affleck is set to take on the role Nick Dunne who is trying to find his wife, who mysteriously disappeared on their anniversary.
Rosamund Pike, Neil Patrick Harris and Missi Pyle are also on the cast list.
This is the first since The Girl with the Dragon Tattoo, as well as being his first collaboration with Affleck.
Gone Girl 3rd October.
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