A man stumbles upon the explosive truth about the life of Jesus, which unleashes a cadre of assassin monks, who work for the Vatican, on his heels to keep the secret quiet.

The man is not Robert Langdon from Dan Brown's best-selling novel The Da Vinci Code, but L. Westminster "Plucky" Purcell from Tom Robbins' 1971 novel Another Roadside Attraction. Purcell actually found the far-from-resurrected body of Christ in the Vatican's basement, and has kidnapped it and is hiding it at a flea circus in Skagit County, Washington. It's a story that would surely exercise the Catholic Church, but it never bothered to protest. However, had director Hal Ashby of Harold and Maude fame actually made the film of Another Roadside Attraction as he'd planned, there would have been nuns in the streets.

Catholics aren't much into banning and burning books anymore; that market has been cornered by low church Protestants, who, it must be said, have a rather touching belief in the power of the written word. But Catholics become rather unglued over films. Whether it's Jean-Luc Goddard's Hail, Mary, Martin Scorsese's The Last Temptation of Christ or Monty Python's The Life of Brian, the wrath of the pope descends upon the local Bijou and strife, along with excellent film publicity opportunities, ensue.

Now the God Squad is wildly firing at the film version of The Da Vinci Code, which, the last time I checked bookshop shelves, was filed under fiction. The basic story of Code is hardly a secret, and has been dealt with in a number of different books, from Holy Blood, Holy Grail to various Romance sagas based in the mists of olde Glastonbury. To wit, Jesus and Mary Magdalene were married, and Mary bore a child that became the bloodline for a royal family.

Brown has spun this yarn into a gripping if plodding suspense potboiler, with a history professor, Robert Langdon, and a young French woman, Sophie, wading through mayhem and murder to find the truth behind the Jesus-Mary union. Along the way, Brown tosses the reader a lot of interesting historical tidbits and plausible (if occasionally counter-factual) theories, many of them Gnostic, which successfully create an alternative to the cobbled-together New Testament.

Ron Howard's film is the visual equivalent of Brown's page-turner. With the exception of the dialogue, which remains true to Brown's wooden original, the film is fast-paced if inadvertently comical at times. Langdon (Tom Hanks) and Sophie (Audrey Tautou) are off on their own desperate Grail quest, dodging killer Franciscans, confused cops and Janus-faced friends en route.

The dialogue is the primary problem. Howard and his screenwriter, Akiva Goldsman, do their level best to cram all of Brown's prodigious pile of scraps into the film, and so there's a lot of information shoved at the viewer. Howard realized the problem at some level, and so has taken the wise decision to fold much of the exposition on historical events into flashbacks. Thus, we find ourselves in Crusader-besieged Jerusalem, the inner sanctum of the Council of Nicaea, even at the funeral of Sir Isaac Newton.

Still, Howard's cast is stuck with often stilted, declamatory lines. Ian McKellen (who, naturally, steals his second film this week) is able to apply his theatrical training to the task to make the words work for him. However, poor Tautou is at sea. The effortless charm and flair she usually brings to her roles is hampered by both the ponderous melodramatics of her script and her uneasiness with English. There's also a coldness between Tautou and the woefully miscast Hanks, and so it's fortunate that we're never asked to believe that they fall in love (they're hardly Audrey Hepburn and Cary Grant in Charade).