Filming of "The Da Vinci Code," starring Tom Hanks and Audrey Tatou, is well under way all across Europe -- but not all the attention is from paparazzi and fans.
In England this week, Sister Mary Michael, a 61-year-old Roman Catholic nun, prayed for 12 hours in protest outside historic Lincoln Cathedral.
That's where Hanks and director Ron Howard were shooting the adaptation of a novel whose plot questions much of Christian theology, proposing that Jesus and Mary Magdalene were married and had a child.
"When I die," Sister Mary Michael said, "and I have to stand before almighty God -- as everyone else will, whether they believe it or not -- and he says to me, 'What have you done to defend me?' I can say, 'Well, I tried to come forward at Lincoln Cathedral.' "
'Contentious and Wayward'
She's not the only one coming forward.
The scene was shot at Lincoln Cathedral rather than Westminster Abbey because Abbey officials refused the filmmakers' request to use their site. They cited the book's "contentious and wayward religious and historic suggestions." So film crews at Lincoln Cathderal re-created Westminster's elaborate screen, the altar, and the grave of Isaac Newton.
Lincoln officials decided it was worth the increased tourism, not to mention a reported donation of 100,000 British pounds (almost $180,000) from the makers of the film.
"It's given us an opportunity to talk to people about 'The Da Vinci Code,' about Westminster Abbey and about Lincoln, and sometimes about the faith that we represent," said John Campbell, an official at Lincoln Cathedral.
It all illustrates what seems an impossible challenge for the filmmakers.
"The Da Vinci Code" has two notable characteristics -- record-breaking sales of more than 25 million books worldwide in 44 languages, and a plot that has been decried by Catholic leaders as heretical.
"It could popularize even further certain distortions of the Christian faith which we think appear in the book," said Monsignor Frank Maniscsalco of the United States Conference of Catholic Bishops. Those include "the fallacies about Jesus' life, questions over his divinity, that he has descendants."
Christian groups, including the United States Conference of Catholic Bishops, have registered protests with Sony Pictures, the studio making the film. The protesters also include the conservative Catholic sect Opus Dei, portrayed in the book as a bunch of thugs.
Can't Please Everyone
So despite the combination of Hanks and Howard, and an almost preposterously successful novel by Dan Brown, the movie is something of a risk.
"In a perfect world, Ron Howard wants to be able to have Dan Brown enthusiastic and to have Pope Benedict enthusiastic," said Michael Medved, the film critic and conservative commentator. "You can't please both of them."
Since the controversy erupted days ago, filmmakers instructed the Rev. Richard P. McBrien, a theology professor at Notre Dame University and a consultant to the film, not to talk to the press. But ABC News spoke with him in March.
"The bottom line is it is a novel," McBrien said. "It is a work of fiction. It isn't a work of history. And for the Vatican or for an archbishop or anyone else to get all upset and excited about it, seems to me, is an excessive reaction."
It is a work of fiction. But religious officials worry readers -- and soon viewers -- will take it as seriously as author Brown seems to.
"I began as a skeptic," Brown told ABC News' Elizabeth Vargas. "As I started researching 'Da Vinci Code,' I really thought I would disprove a lot of this theory about Mary Magdalene and holy blood and all of that. I became a believer."
Thousands of readers seem to be believers, too, or at least curious. They have flocked to locations in the book's plot -- including the Louvre museum in Paris, where a murder sets the hero Robert Langdon onto a trail of mysteries hidden in the great works of Leonardo Da Vinci, and historic churches like Saint-Sulpice. Perhaps they are pursuing what the book depicts as secrets that some in the Catholic church are willing to kill to protect.
Next month, the cast and crew shoot the film's climax in Scotland's Rosslyn Chapel. Because of the "Da Vinci Code" book, it's a place that has seen foot traffic triple in the last two years -- to the point that experts are worried about irreparable damage to the chapel's delicate stone carvings. It is a place where interest in Christianity has significantly increased, but not without a cost.
Tackling Controversial Theories
Those offended by "The Da Vinci Code" are not only put off by the portrayal of Catholic officials as conspiratorial, corrupt, misogynistic and homicidal, but by the notion that so much of Christian teaching is untrue -- that, for instance, Jesus was married. Or that, as Brown asserts in the book, the Holy Grail is not a chalice, but Mary Magdalene herself, carrying Jesus' child, and that she was his most important apostle, as portrayed in Da Vinci's painting, "The Last Supper."
"If you look at the right hand of Jesus, there is the Holy Grail, and her name is Mary Magdalene," Brown said.
Maniscsalco can't believe people accept such theories as plausible.
"That painting is solidly in the tradition of Renaissance art, where men are often portrayed as androgynously beautiful," he said. "It's just amazing that people take so seriously facts that I would reject out of hand."
With the controversy raging, some wonder if the filmmakers will compromise the book's plot.
"They're left with one feeble alternative," Medved said, "which I call the 'Miracle on 34th Street' approach -- which is 'Well, maybe he is Santa Claus and maybe he isn't Santa Claus.' And in this case this would be, 'Well, this is an interesting theory; we don't know if it's true or not.'
"A lot of people who love the book will be offended by that, because it will be seen as wimping out," Medved added.
McBrien suggested there will be some modifications -- though no one else affiliated with the film would discuss its content or any changes.
"You always hear people say after the film is over, 'Well it wasn't like the novel,' … and that's going to happen in the case of 'The Da Vinci Code,'" McBrien said. "There are going to be some things in there that may have been regarded as gratuitously offensive to Catholics, or others that will be muted or taken out."