The document summarizes the plot of Dan Brown's novel The Da Vinci Code. It follows symbologist Robert Langdon and cryptologist Sophie Neveu after the murder of Louvre curator Jacques Saunière. They become involved in a battle between the secret societies Priory of Sion and Opus Dei over the possibility that Jesus Christ had a companion in Mary Magdalene. The cryptic clues left by Saunière lead Langdon and Neveu on a quest to uncover the secret behind the Holy Grail.