There in the bowels of the Louvre... with images of PHI and Da Vinci swirling through his mind, Robert Langdon suddenly and unexpectedly deciphered Saunière's code.

"O, Draconian devil!" he said. "Oh, lame saint! It's the simplest kind of code!"

Sophie was stopped on the stairs below him, staring up in confusion. A code? She had been pondering the words all night and had not seen a code. Especially a simple one.

"You said it yourself." Langdon's voice reverberated with excitement. "Fibonacci numbers only have meaning in their proper order. Otherwise they're mathematical gibberish."

Sophie had no idea what he was talking about. The Fibonacci numbers? She was certain they had been intended as nothing more than a means to get the Cryptography Department involved tonight. They have another purpose? She plunged her hand into her pocket and pulled out the printout, studying her grandfather's message again.

13-3-2-21-1-1-8-5