Dan Brown's novel sold roughly 80 million copies and turned Leonardo da Vinci's paintings into supposed treasure maps for a secret bloodline descended from Jesus. This DW documentary sends art historians, religious scholars, and researchers of medieval conspiracy theories back to the sources Brown drew on, checking his claims about the Priory of Sion, the Knights Templar, and hidden symbols in works like The Last Supper against the actual historical record. Clips from the 2006 film adaptation with Tom Hanks appear alongside the expert interviews, and the film revisits the Catholic Church's furious reaction and the boycott calls the book provoked on release. Rather than simply debunking or endorsing the novel's premise, the documentary traces where each idea actually originated, some in genuine medieval legend, others invented wholesale for the plot, and shows how thoroughly fiction and scholarship got tangled together in the public imagination. The picture that emerges of the real history behind the myth is stranger, and messier, than the neat conspiracy Brown packaged for readers.