The Da Vinci Code

CHAPTER 48

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Langdon could scarcely believe his own supposition, and yet, considering who had given this stone 
cylinder to them, how he had given it to them, and now, the inlaid Rose on the container, Langdon 
could formulate only one conclusion.
I am holding the Priory keystone.
The legend was specific.
The keystone is an encoded stone that lies beneath the sign of the Rose.
"Robert?" Sophie was watching him. "What's going on?"
Langdon needed a moment to gather his thoughts. "Did your grandfather ever speak to you of 
something called la clef de voûte?"
"The key to the vault?" Sophie translated.
"No, that's the literal translation. Clef de voûte is a common architectural term. Voûte refers not to a 
bank vault, but to a vault in an archway. Like a vaulted ceiling."
"But vaulted ceilings don't have keys."
"Actually they do. Every stone archway requires a central, wedge-shaped stone at the top which 
locks the pieces together and carries all the weight. This stone is, in an architectural sense, the key 
to the vault. In English we call it a keystone." Langdon watched her eyes for any spark of 
recognition.
Sophie shrugged, glancing down at the cryptex. "But this obviously is not a keystone."
Langdon didn't know where to begin. Keystones as a masonry technique for building stone 
archways had been one of the best-kept secrets of the early Masonic brotherhood. The Royal Arch 
Degree. Architecture. Keystones. It was all interconnected. The secret knowledge of how to use a 
wedged keystone to build a vaulted archway was part of the wisdom that had made the Masons 
such wealthy craftsmen, and it was a secret they guarded carefully. Keystones had always had a 
tradition of secrecy. And yet, the stone cylinder in the rosewood box was obviously something 
quite different. The Priory keystone—if this was indeed what they were holding—was not at all 
what Langdon had imagined.
"The Priory keystone is not my specialty," Langdon admitted. "My interest in the Holy Grail is 
primarily symbologic, so I tend to ignore the plethora of lore regarding how to actually find it."
Sophie's eyebrows arched. "Find the Holy Grail?"

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Langdon gave an uneasy nod, speaking his next words carefully. "Sophie, according to Priory lore, 
the keystone is an encoded map... a map that reveals the hiding place of the Holy Grail."
Sophie's face went blank. "And you think this is it?"
Langdon didn't know what to say. Even to him it sounded unbelievable, and yet the keystone was 
the only logical conclusion he could muster. An encrypted stone, hidden beneath the sign of the 
Rose.
The idea that the cryptex had been designed by Leonardo da Vinci—former Grand Master of the 
Priory of Sion—shone as another tantalizing indicator that this was indeed the Priory keystone. A 
former Grand Master's blueprint... brought to life centuries later by another Priory member. The 
bond was too palpable to dismiss.
For the last decade, historians had been searching for the keystone in French churches. Grail 
seekers, familiar with the Priory's history of cryptic double-talk, had concluded la clef de voûte was 
a literal keystone—an architectural wedge—an engraved, encrypted stone, inserted into a vaulted 
archway in a church. Beneath the sign of the Rose. In architecture, there was no shortage of roses. 
Rose windows. Rosette reliefs. And, of course, an abundance of cinquefoils—the five-petaled 
decorative flowers often found at the top of archways, directly over the keystone. The hiding place 
seemed diabolically simple. The map to the Holy Grail was incorporated high in an archway of 
some forgotten church, mocking the blind churchgoers who wandered beneath it.
"This cryptex can't be the keystone," Sophie argued. "It's not old enough. I'm certain my 
grandfather made this. It can't be part of any ancient Grail legend."
"Actually," Langdon replied, feeling a tingle of excitement ripple through him, "the keystone is 
believed to have been created by the Priory sometime in the past couple of decades."
Sophie's eyes flashed disbelief. "But if this cryptex reveals the hiding place of the Holy Grail, why 
would my grandfather give it to me? I have no idea how to open it or what to do with it. I don't 
even know what the Holy Grail is!"
Langdon realized to his surprise that she was right. He had not yet had a chance to explain to 
Sophie the true nature of the Holy Grail. That story would have to wait. At the moment, they were 
focused on the keystone.