 Their book concludes that the Prieuré de Sion, via the Knights Templar, guarded the Merovingian bloodline, that this dynasty descended from a supposed marriage of Jesus Christ and Mary Magdalene, and that Pierre Plantard was a modern-day descendant; it suggested that Saunière may have discovered that secret and amassed his wealth through blackmail of the Holy See.Despite its popularity, historians think the book advances faulty premises and that several of its arguments merit questioning.The bloodline hypotheses of Lincoln, Baigent and Leigh were later picked up in 2003 by Dan Brown's bestselling novel "The Da Vinci Code".