By EW Staff
December 11, 2007 at 05:00 AM EST

While making her first-ever action-adventure film, Oscar winner Helen Mirren had to scamper up rock faces, swing from wires across vast abysses, and plunge into water tanks that left her half-drowned. So how did the onetime Queen of England — cast here as the mother of treasure hunter Ben Gates (Nicolas Cage) — take to a full-on Jerry Bruckheimer production? ”Everything we did that had action, she was the first one to jump in,” says Jon Voight, who plays Mirren’s estranged ex. ”She was like a kid, I tell you. A kid!” Definitely a nice change from panty hose and kilts. ”I absolutely loved every minute,” Mirren says. ”[After my first stunt], I said to the director that it was the best day of my professional life.”

All this derring-do is launched by a scrap of one of the 18 pages missing from John Wilkes Booth’s diary (a historical fact), which implicates a Gates ancestor in Abraham Lincoln’s assassination. Ben discovers that to exonerate his great-great-grandfather, he must track down a top secret tome passed down from president to president called the Book of Secrets (a historical fiction). Oh, and kidnap the Commander-in-Chief (Bruce Greenwood). That, too.

”The weird thing with [planning] how you would kidnap the president is you find yourself consulting with people who have criminal knowledge,” says Turteltaub (who also directed the first National Treasure). As well as the fine folks who run Mount Vernon, George Washington’s Virginia home. ”[The abduction] involves very specific knowledge about the architecture and the secret tunnels,” says Turteltaub. Even the Secret Service happily advised the filmmakers on how they would handle someone nabbing their charge. ”They’re so aware of how the movie business works,” laughs Turteltaub. ”You end up getting notes on character and story. Often, they’re pretty good.”

With the movie still in production, it’s too soon to be thinking about another sequel, but Mirren, for one, would be game. ”It is a very different approach to filmmaking,” she chuckles. ”The script was an ever-moving target, never an absolutely fixed thing…. I’ve said to Jerry, ‘Please, if you’ve got any more like this, knock on my door!”’ We can see it now: The Queen 2: Curse of the Crown Jewels.