In the Louvre, a monk of Opus Dei named Silas apprehends Jacques Sauniere, the museum's curator, and demands to know where the Holy Grail is. After Sauniere tells him, Silas shoots him and leaves him to die. However, Sauniere has lied to Silas about the Grail's location. Realizing that he has only a few minutes to live and that he must pass on his important secret, Sauniere paints a pentacle on his stomach with his own blood, draws a circle with his blood, and drags himself into the center of the circle, re-creating the position of Da Vinci's Vitruvian Man. He also leaves a code, a line of numbers, and two lines of text on the ground in invisible ink.
A police detective, Jerome Collet, calls Robert Langdon, the story's protagonist and a professor of symbology, and asks him to come to the Louvre to try to interpret the scene.
Langdon does not yet realize that he himself is suspected of the murder. After murdering Sauniere, Silas calls the "Teacher" and tells him that, according to Sauniere, the keystone is in the Church of Saint-Suplice in Paris. The Teacher sends Silas there. Silas follows Sauniere's clues to the keystone's location and discovers that he has been tricked. In a fit of rage, he kills Sister Sandrine Bieil, the church's keeper and a sentry for the Priory of Sion. At the Louvre, Langdon meets Jerome Collet and Bezu Fache, the police captain, and realizes that the two policemen suspect him of the murder.
Sophie Neveu, an agent of the department of cryptology and Sauniere's granddaughter, arrives at the crime scene and tells Langdon that he must call the embassy. When Langdon calls the number Sophie gave him, he reaches her answering service. The message warns Langdon that he is...