Flynn spoke to Entertainment Weekly about penning the screenplay adaptation to her 2012 best-selling novel, revealing that readers who were unhappy with the book's divisive ending may be in for a treat when the film comes out in theaters on Oct. 3.
"There was something thrilling about taking this piece of work that I'd spent about two years painstakingly putting together with all its eight million Lego pieces and take a hammer to it and bash it apart and reassemble it into a movie," Flynn told EW.
The film stars Ben Affleck and Rosamund Pike as Nick and Amy -- two married unemployed magazine writers, who settle in the countryside after leaving New York behind them. Things eventually turn sour and, on their 5th wedding anniversary, Nick becomes a potential murder suspect when his wife mysteriously vanishes.
Flynn, a former writer for EW, wouldn't reveal exactly what she changed, but she did say that viewers should expect major alterations, after readers were divided by the book's conclusion.
"Ben was so shocked by it," Flynn said (per Time). "He would say, 'This is a whole new third act! She literally threw that third act out and started from scratch.'"
In a rare move, Affleck and Pike appear on the magazine's cover in a photo shot by the movie's director, acclaimed two-time Oscar-nominee David Fincher, known for films like "The Social Network," "The Curious Case of Benjamin Button," "Fight Club" and "Se7en."
Flynn's changes don't seem to bother Fincher, who told EW that when it came to adapting Stieg Larson's "The Girl With The Dragon Tattoo" in 2011, "we may have been too beholden to the source material."
Read more in the latest issue of EW, now available on newsstands.
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