Fans of the novel Gone Girl might be in for a big surprise when the movie version is released later this year: author Gillian Flynn has rewritten the entire final act for the movie.

The film adaptation of the bestselling novel is directed by David Fincher, and stars Ben Affleck and Rosamund Pike as the toxic married couple Nick and Amy Dunne. It’s unclear just how the ending will differ on-screen, but Flynn—who wrote both the novel and the screenplay—hinted in an interview to Entertainment Weekly that the change is drastic. “Ben was so shocked by it,” Flynn told EW. “He would say, ‘This is a whole new third act! She literally threw that third act out and started from scratch.’”

Depending on how readers interpreted the original, polarizing ending, the change could be welcome. For Flynn’s part, she apparently had no problem with changing her work. She told EW, “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.”

The film hits theaters on Oct. 3.

[Entertainment Weekly]