For most of the last 2,000 years, the Catholic Church called Mary Magdalene a prostitute who gave up her sinful life to follow Jesus.
But some people believe that Mary Magdalene was maligned through the centuries, and that she actually played a much more significant role in Jesus' life: as his wife, the mother of his child, and the most important of his disciples.
The truth, they believe, was deliberately suppressed by church leaders. There is a theory that the truth about Mary was kept alive by a secret society known as the Priory of Sion, whose members included some of the greatest artists and thinkers of Western civilization, including Leonardo Da Vinci.
Author Dan Brown believes the renaissance master encoded the truth in some of his most famous paintings. His best-selling book, The Da Vinci Code, has a lot of people talking these days. The book is a novel, but author Dan Brown says much if it is drawn from historical evidence.
To investigate some of the claims in the book, ABCNEWS' Elizabeth Vargas traveled from one edge of the Mediterranean to the other. She found that not all the claims in the book are credible, but that some of them appear to have elements of truth.
The depiction of Mary Magdalene as a prostitute has its origins in interpretations of Luke's gospel, where it says she was cured of seven demons.
She's also introduced Luke right after a story about a prostitute whom Jesus forgives for her sins. In the year 591, Pope Gregory the Great overlapped the two identities.
The Vatican eventually corrected that impression, but not until 1969, 1,378 years later.
Brown believes the church allowed the confusion to obscure the truth about Mary's relationship with Jesus.
Scholars said the confusion has eclipsed important information the Bible does provide about Mary Magdalene.
"She's perhaps the most frequently mentioned woman who is among the followers of Jesus in the Gospels of the New Testament," said Biblical scholar Elaine Pagels.
The Rev. Richard McBrien of Notre Dame University said he thinks Mary Magdalene would have been recognized as one of Jesus' main apostles — and possibly the key apostle — had she been a man.
Margaret Starbird, who wrote several books that Dan Brown relied upon in writing The Da Vinci Code, said the Bible suggests she might have been Jesus' wife.
The Gospel according to John tells the story of a woman named Mary who anoints Jesus' feet with oil and wipes it away with her hair which is a marriage ritual, she said. And even though the woman is identified as Mary of Bethany, not Mary Magdalene, Starbird believes they are the same person.
In his novel, Brown says there is an apparent omission in Leonardo Da Vinci's famous painting "The Last Supper": the Holy Grail, or the chalice from which the disciples allegedly drank their wine, is missing, he said.
But he says the Holy Grail actually is there, on the right hand of Jesus. He says the grail is the figure to the right of Jesus — commonly thought to be John, but actually Mary Magdalene.
Some versions of the legend of the Holy Grail say it was taken out of Jerusalem and hidden away in Europe for centuries. Another legend holds that Mary Magdalene arrived on the coast of Provence in southern France with a boatload of Jesus' followers sometime after the crucifixion.
Mary and the others were said to have brought the grail with them — a symbolic way of saying that Jesus' child had come with them, Starbird said.
In Leonardo's painting, the figure is wearing the same color as Jesus — possibly indicating a special relationship, Brown said. He said the way the figure is aligned with Jesus also forms a V, a symbol of the feminine long before Leonardo's time.
Many art historians have dismissed the theory that the figure is a woman, saying it's just a tradition to paint John as beardless and long-haired. "It looks like a young male. I see no breasts," art historian Jack Wasserman told ABCNEWS.
But Carlos Pedretti, one of the world's leading Leonardo experts and head of the Leonardo Institute in Florence offered a rare word of agreement, noting that a portrait of the figure next to Jesus, sketched by one of Leonardo's top students, clearly appears to be a woman.
Stories about the Priory of Sion first surfaced in the modern era during the late 1960s, when a set of documents was discovered deep in the French National Library that made numerous references to the supposed society.
The documents outlined a family tree that went back to the Merovingian Kings, monarchs who ruled in the south of France from the 6th to the 8th century.
According to Henry Lincoln, who co-authored the 1983 book, Holy Blood, Holy Grail with Michael Baigent and Richard Leigh, the Merovingian legends say the first king's mother was said to have been impregnated by a sea creature. One of the earliest symbols for Jesus and Christianity was a fish.
Holy Blood, Holy Grail suggests that the Merovingian kings were the descendants of Jesus and Mary Magdalene, and that their descendants founded the Priory of Sion. The book argued that the Knights Templar, an order that really existed in the 12th century, originated as the military wing of the Priory of Sion.
In the earliest written versions of the legend of the knights of the Holy Grail, the knights were called Templaisers, which historians think actually refer to the Knights Templar.
"They were referred to as the Guardians of the Grail and of the Grail Family. They were there to protect that royal family," said Lincoln.
The Knights Templar existed for 200 years, but were suddenly rounded up one day by King Phillip of France, accused of heresy and executed by the priests of the Inquisition.
One theory is that the Knights Templar were destroyed because during the crusades, they might have brought back evidence from the Middle East that proved the identity of Mary Magdalene and her descendants, Brown said.
Although Brown based his novel around the legend of the Priory of Sion, he is not sure himself whether the mysterious society really existed or is a modern fabrication. "I don't think we'll ever know," he said.
Using the Priory of Sion documents from the French library, ABCNEWS found a pair of noble-born Scottish cousins named Andrew and Niven Sinclair.
Their ancestor William Sinclair built the Roslyn Chapel in Scotland — often referred to in the legends of King Arthur as the Chapel of the Grail.
As far as their holy roots, Andrew doesn't put much stock in the legend. "There's no proof that actually this is a bloodline of Mary Magdalene and Jesus," he said.
Niven Sinclair does think they married into the Jesus bloodline. But, he said, "by the time it gets to me, it will be very, very, very diluted."
The discovery of some scrolls in Egypt in 1945 provided a source for what Brown calls "an alternative history."
It's believed that the Nag Hammadi scrolls were originally hidden by a monk in the late 4th century, at the same time the bishop of Alexandria ordered them destroyed.
The writings are sometimes called the Gnostic Gospels. "Gnostic" means knowledge, and the groups who wrote them often claimed special knowledge about Jesus.
One of the 50-odd texts contains a line stating that Mary Magdalene was Jesus' favorite and he often kissed her on the mouth, according to Brown. However, the parchments are so damaged that it's hard to be sure what kind of kiss the document is describing.
The texts also identify Mary Magdalene as the companion of Jesus. Brown believes the term means she was Jesus' wife.
Even outside the Gnostic Gospels there is evidence that in the first centuries after Jesus, Mary Magdalene was treated with great respect by several of the early church leaders who were men.
By the year 200 though, women were systematically excluded from any positions of authority, said Pagels. "Throughout history, our history books have been written by the winners," Brown said.
Brown recognizes his book has touched a nerve by dealing with topics that have been forbidden for centuries.
"These are topics that resonate at a deep, deep spiritual level — really at the core of the human psyche," he said.
"Whether you agree or disagree with the topics — they're on the table, and we're talking about them, and these are topics that for centuries have been taboo."