Chapter 31
Chapter Characters:
Sister Sandrine
Silas, the albino monk

Chapter Summary:
Sister Sandrine calls all four numbers, but she finds the first three contacts are dead and leaves a message at the fourth: "'The floor panel has been broken!' … 'The other three are dead!'" Sister Sandrine does not know the identies of the contacts but was told to place the calls under one condition: "If that floor panel is ever broken, the faceless messenger had told her, it means the upper echelon has been breached. One of us has been mortally threatened and been forced to tell a desperate lie. Call the numbers. Warn the others. Do not fail us in this."

Silas confronts Sister Sandrine and tells her that all four contacts are dead. He demands that she tell him where the keystone is and says, "'You are a sister of the Church, and yet you serve them?'" She tells him that "'Jesus had but one true message … I cannot see that message in Opus Dei.'" Denying him both information and hope, Silas kills her.

Chapter Themes:
The human world is encoded with meaning.
The centrality of human relationships, especially male-female relationships.
The power of belief, and the need to believe.

Chapter 32
Chapter Characters:
Robert Langdon
Sophie Neveu

Chapter Summary:
Sophie and Langdon get into her SmartCar and race through Paris towards the U.S. Embassy. As they do, she remembers again that fateful night when she accidentally surprised her grandfather in the midst of a masked pagan ceremony, thereby learning a secret about him that makes her cut off all contact.

The chapter ends with the road to the embassy blocked by French police, who give chase as Sophie turns around and speeds away.

Chapter Themes:
The centrality of human relationships, especially male-female relationships.
The influence of the past upon the present.

Chapter 33
Chapter Characters:
Robert Langdon
Sophie Neveu

Chapter Summary:
As she drives, Sophie shows Langdon the key her grandfather left behind the Madonna of the Rocks. Langdon inspects the key, explaining its relation to the Priory of Sion with its fleur-de-lis and the initials P.S. He wonders if the key has anything to do with the Priory's reason for existence: the protection of a powerful secret. Langdon tells Sophie that the shape of the head of the key, a square cross with equal arms, predates Christianity. It is considered a "peaceful" cross because its shape was not good for crucifications. The balanced shape also reflects the Priory philosphy of the union of male and female.

Sophie drives them to Gare Saint-Lazare; the chapter ends with them planning to buy two train tickets out of Paris.

Chapter Themes:
The human world is encoded with meaning.
The centrality of human relationships, especially male-female relationships.
The influence of the past upon the present.

Chapter 34
Chapter Characters:
Bishop Aringarosa

Chapter Summary:
A driver in an unmarked Vatican car picks up Bishop Aringarosa at Leonardo da Vinci International Airport. He drives Aringarosa to Castel Gandolfo, which is the Pope's summer residence and also houses the Specula Vaticana (the Vatican Observatory). Aringarosa recalls his last trip there five months earlier when he learned the shocking news that he had a six-month timeline to complete his plans.

In present time, Aringarosa wonders why the Teacher has not called him, as Silas should now have the keystone. As he touches the ring on his finger, "he reminded himself that this ring was a symbol of power far less than that which he would soon attain."

Chapter Themes:
The power of belief, and the need to believe.
The influence of the past upon the present.

Chapter 35
Chapter Characters:
Robert Langdon
Sophie Neveu

Chapter Summary:
At Gare Saint-Lazare, Langdon and Sophie buy two train tickets with his credit card, so that the police will be notified and think he has fled the city. As they leave the station in a taxi, Langdon finds an address, 24 Rue Haxo, written on the key in black-light pen.

Sophie asks Langdon to tell her everything he knows about the Priory of Sion.

Chapter Themes:
The human world is encoded with meaning.
The centrality of human relationships, especially male-female relationships.
The influence of the past upon the present.

Chapter 36
Chapter Characters:
Bezu Fache
Jerome Collet
Claude Grouard

Chapter Summary:
Back at the Louvre, Grouard briefs Fache on Sophie and Langdon's escape. Collet reports that Sophie and Langdon have been traced to the train station, but Fache thinks it is a decoy. They plan their search for the fugitives; Fache expects to capture them by morning.

Chapter Themes:
The centrality of human relationships, especially male-female relationships.
The power of belief, and the need to believe.

Chapter 37
Chapter Characters:
Robert Langdon
Sophie Neveu

Chapter Summary:
Langdon and Sophie's taxi goes through the Bois de Boulogne, a park nicknamed "the Garden of Earthly Delights" after the Bosch painting; it is a place where perversion happens. As they drive through it, Langdon explains the history of the Priory of Sion, starting with its founding in Jerusalem in 1099 by French king Godefroi do Bouillon after he conquered the city. He charged them with protecting and passing on a secret long held by his family since the time of Christ. The Priory learned of certain crucial secret documents, which they thought confirmed King Godefroi's secret, hidden beneath the ruins of Herod's temple. The documents were so important that the Catholic Church wanted them very badly. The Priory founded the Knights Templar to get these documents.

Langdon explains that the Knights found something that made them rich and powerful. The Church first gave the Knights unlimited power, then on Friday, October 13, 1307, moved against them to obtain their secret treasure, almost obliterating them. But the secret documents had already been given to the Priory of Sion to guard and protect. Langdon argues that the Knights had found the Sangreal—the Holy Grail.

Chapter Themes:
The human world is encoded with meaning.
The centrality of human relationships, especially male-female relationships.
The power of belief, and the need to believe.
The influence of the past upon the present.

Chapter 38
Chapter Characters:
Robert Langdon
Sophie Neveu

Chapter Summary:
When Sophie challenges Langdon about the secret nature of the Holy Grail, which she says is a cup that Jesus drank from at the Last Supper and that caught his blood when he was crucified, Langdon tells her that the cup or chalice is only a metaphor. This starts a chain of memory as Langdon remembers proposing his most recent book to his editor.

Sophie interrupts Langdon's memories by shouting at the taxi driver, who was starting to speak into his radio, which had just announced them as fugitives. Sophie forces the man out of the taxi and tells Robert to drive. He does, but badly, as he does not know how to drive a stick shift.

Chapter Themes:
The human world is encoded with meaning.
The centrality of human relationships, especially male-female relationships.
The influence of the past upon the present.

Chapter 39
Chapter Characters:
Silas, the albino monk

Chapter Summary:
Alone in his room, Silas reflects on how badly his search for the keystone has gone, and whips himself as a sign of his dedication.

Chapter Themes:
The power of belief, and the need to believe.

Chapter 40
Chapter Characters:
Robert Langdon
Sophie Neveu

Chapter Summary:
As Sophie and Langdon drive, Langdon wonders if the key will lead them to the Holy Grail. Earlier, he had realized the square cross is also a symbol of the Knights Templar, and the Holy Grail is believed to be hidden beneath a Templar church. However, Langdon tells Sophie that the location of the Holy Grail is so secret that only four top members of the Priory of Sion know at one time it's hiding place—the Grand Master and his three sénéchaux; even if her grandfather had been in such a high position, he could never tell her the secret because she was not in the brotherhood. But Sophie thinks, "My grandfather was one of them … I've already been there," as she remembers the ritual she had witnessed ten years ago.

Langdon and Sophie find their way to 24 Rue Haxo, which is a Depository Bank of Zurich: the key is for a Swiss bank deposit box.

Chapter Themes:
The human world is encoded with meaning.
The influence of the past upon the present.