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 in danger and should meet Sophie in the bathroom at the Louvre.In the bathroom, Sophie shows Langdon that Fache is noting his movements with a tracking device. She throws the device out the window onto a passing truck, tricking the police into thinking that Langdon has escaped from the Louvre.Sophie also tells Langdon that the last line in the secret message, “P.S. Find Robert Langdon,” was her grandfather’s way of alerting her: P.S. are the initials of her grandfather’s nickname for her, Princesse Sophie. Langdon thinks that P.S. might stand for Priory of Sion, an ancient brotherhood devoted to the preservation of the pagan goddess worship tradition, and to the maintenance of the secret that Sauniere died protecting.