Despite all of the breathtaking artwork hanging on the walls, Langdon is more impressed with the fancy-shmancy floor in the Grand Gallery.
He's also mighty miffed about the Caravaggio just lying there on the fancy floor. Fache explains that Saunière pulled it down to activate the security gate, separating him from his attacker.
The dim, noninvasive lighting used at night in the Louvre reminds Langdon of his adventures in the Vatican last year (covered in Dan Brown's novel Angels and Demons), and of Vittoria, who's gone MIA from his life. Sad face.
Fache explains to Langdon that Saunière took about fifteen to twenty minutes to die from the bullet wound to his stomach. In that time he was able to do a ton of stuff, like arrange his corpse in a bizarre manner.
Saunière is naked, arms and legs spread out as if he were making a snow angel on the fancy floor. He had used his own blood to draw a pentacle (a five-pointed star) on his own stomach.
Fache jumps to the obvious conclusion that the pentacle's a sign of devil worship, but you bet your boots that Langdon corrected him on this grave error.
The pentacle used to be a symbol representing the sacred feminine and Venus before the Catholic Church launched a smear campaign in order to delegitimize pagan symbols.
Fache wants to know why Saunière had to be nude. And why he used his own blood as ink.
Langdon thinks that he didn't have anything else to write with…until Fache points out that Saunière died clutching a felt-tipped marker.
It's a black-light pen, used by museums to place invisible marks on items (using noncorrosive, alcohol-based fluorescent ink visible only under black light) to identify paintings that needed restoration.
Fache turns off the lights and grabs a black light. What's illuminated shocks Langdon.
Meanwhile, in Saunière's office, Lieutenant Collet's listening in on Fache and Langdon's recorded conversation, gleefully anticipating the big "moment of truth".