George Lucas has said that he is yet to find the 'MacGuffin' - the plot device - for Indiana Jones 5.
The writer and producer is still working on the details for the movie's story, including trying to find its "Holy Grail."
Speaking to New York Magazine, Lucas said that Steven Spielberg's claims that the concept is now settled isn't quite true, explaining: "Actually, I told him I didn't have it yet. I told him about the story, but I really haven't found the MacGuffin yet.
"I mean, I know what it's about, but I just have to find a MacGuffin that fits into the arena we’re working in."
A term created by Alfred Hitchock, a MacGuffin is a storytelling device that drives the plot and draws attention, but isn't of any real significance.
Each of Indiana Jones's adventures has been based around this concept.
Harrison Ford has confirmed that he will be returning for a fifth Indy installment.
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