As Silas arrives at Saint-Sulpice, he reflects on his past. He ran away from home at a young age after murdering his abusive father and continued to live a life of violence. He was in prison for murder when an earthquake opened a big hole in the wall of his cell. When he ran, he ended up at a church in Oviedo, Spain. Aringarosa, then a missionary, saved him and gave him the name Silas, after a passage in the Bible. From that point on Silas became deeply devout. He is now Aringarosa’s faithful righthand man.
On the plane, Bishop Aringarosa thinks about how Opus Dei offered the Teacher a large amount of money for information about the location of the keystone. The Teacher told Aringarosa that he must not be in contact with Silas, presumably in order to maintain secrecy and throw the police off the scent.
As Langdon listens to Sophie’s message, Sophie tells Fache that if put in ascending order, the numbers next to Saunière’s body form the Fibonacci sequence, a progression in which each term is equal to the sum of the two preceding terms. If Sophie is right, the code was a cryptographic joke. Unsatisfied with Sophie’s interpretation, Fache grows even angrier. Sophie leaves, and Langdon tells Fache that according to the embassy, a friend has had an accident. Langdon goes to the restroom after saying he isn’t feeling well and would like to be alone. Collet and Fache track him electronically. Fache tells Collet to make sure Langdon doesn’t leave the gallery.
Sophie meets Langdon in the bathroom to explain her message further. She tells him that he is a suspect, and that a GPS tracker has been planted on him. After rummaging in his pocket, Langdon finds a tracker and realizes it must have been planted on him at the hotel. Langdon’s first impulse is to throw the tracker away, but Sophie convinces him that a static dot on the tracking screen would immediately arouse police suspicion. She shows him a picture of the crime scene that Fache uploaded to her departmental website. Fache photographed a line and then erased before Langdon’s arrival, but the line is visible in the picture. It reads, “P.S. Find Robert Langdon.”
Sophie tells Langdon that the police have more than enough evidence to arrest him for the murder, but she knows that he is innocent. She believes Saunière was telling her to look for him. Saunière knew that The Vitruvian Man was her favorite Da Vinci drawing. He also must have known that if he put numbers into the message on the floor, the cryptography department would get involved with the investigation. Also, she thinks that the “P.S.” in the message “P.S. Find Robert Langdon” stands for Princesse Sophie, his nickname for her. Langdon is confused about Sophie’s connection to Saunière. He suspects that Sophie may have been Saunière’s mistress until she tells him that Saunière was her grandfather, but that they’d had a falling-out.
Ten minutes have gone by. Fache and Collet wonder why Langdon has not returned from the bathroom. Collet tells Fache that Langdon is not onto their plan. The tracking dot is showing slight movements, indicating that it is still on his body. If Langdon had found the device, he would have removed it and tried to run.
Collet thinks that Fache is unusually invested in this case, probably because Fache has recently suffered a some bad public relations and needs a high-profile arrest to secure his position. The director of the cryptology department calls. He wants to talk to Fache about Sophie Neveu.
Silas moves toward the Church of Saint-Sulpice. He sees some teenage prostitutes on the plaza. The lust he feels is immediately smothered by the pain of the punishment belt around his thigh. Silas has taken a vow of celibacy for Opus Dei, a vow he sees as a small price to pay for salvation, especially considering the sexual assault he endured in prison. Prepared to retrieve the keystone, he knocks on the door of the church.
Silas’s conversion to Christianity sprung from his first experience of kindness. Aringarosa was willing to shelter and care for Silas despite Silas’s dark past. Such unconditional support, so new to Silas, has made Silas devoted to Aringarosa and willing to believe everything Aringarosa tells him. Silas seems totally willing to return to his violent tendencies, this time under the pretext of religion and furthering Opus Dei. At this point, it is not entirely clear whether Aringarosa is taking advantage of Silas to further his own plans.
Fache’s connection to Opus Dei is unclear. He is a pious Catholic who has been known to mix church and state affairs, and Brown makes us wonder whether he is in on the keystone conspiracy. On one hand, Fache genuinely seems to believe that Langdon is guilty of Saunière’s murder. On the other hand, it is possible that Fache’s seeming belief is actually just an act for Collet’s sake, and that Fache is setting Langdon up.
Like Opus Dei, Fache is prejudiced toward women. His contempt for women works to his disadvantage—by underestimating Sophie’s intelligence, he allows himself to be tricked. It seems obvious that Sophie is up to something, but Brown means for the reader to believe that the strength of Fache’s prejudice prevents him from seeing what is actually going on.
The strength of Sophie’s faith in Langdon’s innocence is slightly puzzling, but it might simply be a reflection of her good instincts. The dynamic between Sophie and Langdon will be one of the driving interpersonal forces of the novel as both of them embark on a mission of discovery. If Sophie is right that Saunière wrote the code and message in order to bring her and Langdon together, it must be because Saunière thought that together the pair could uncover his secret.