"You certainly seem to be enjoying those niches!" the docent said, looking delighted. "Were you aware that the tapering thickness of the walls is the reason the dome appears weightless?"

Langdon's progress around his side of the Pantheon was being hampered somewhat by the guide on his heels, now continuing his tireless narration as Langdon prepared to check the final alcove.

Langdon nodded, not hearing a word as he prepared to examine another niche. Suddenly someone grabbed him from behind. It was Vittoria. She was breathless and tugging at his arm. From the look of terror on her face, Langdon could only imagine one thing. She found a body. He felt an upswelling of dread.

"Ah, your wife!" the docent exclaimed, clearly thrilled to have another guest. He motioned to her short pants and hiking boots. "Nowyou I can tell are American!"

Vittoria's eyes narrowed. "I'm Italian."

The guide's smile dimmed. "Oh, dear."

"Robert," Vittoria whispered, trying to turn her back on the guide. "Galileo"sDiagramma. I need to see it."

Vittoria deciphered the number. "1639?"

Vittoria's eyes filled with foreboding. "We're in trouble, Robert. Big trouble. The dates don't match."

"Date," Vittoria repeated to Langdon. "When did Galileo publish…"

"Could you excuse us?" Langdon said. He was confused by Vittoria's panic. He took her aside and reached in his pocket, carefully extracting theDiagramma folio. "What's going on?"

"Tourist reproduction," Langdon quipped. "Thank you for your help. Please, my wife and I would like a moment alone."

"Diagramma?"the docent said, wheedling back in. "My! You two certainly know your history! Unfortunately that document is not viewable. It is under secret preservation in the Vatican Arc --"

"Yes. What's wrong?"

Langdon pointed to the Roman numeral in the lower liner. "That's the pub date. What's going on?"

"What's the date on this thing?" Vittoria demanded, scanning the sheet.

The docent was on them again, staring at the folio, mouth agape. "That's not… really…"

The docent backed off, eyes never leaving the paper.

"Urb… Urbino," he stammered, now looking bewildered. "His birthplace."

Vittoria ran over and grabbed the docent, pulling him back. "Signore, excuse us. Where was Raphael's body in the 1600s?"

Langdon was lost. "What are you talking about?"

Langdon could not breathe. "But that… means…"

"Yes, but he wasn't buriedhere until much later."

"I just read it. Raphael's body was relocated to the Pantheon in 1758. It was part of some historic tribute to eminent Italians."

"Yes! It means we're in the wrong place!"

As the words settled in, Langdon felt like a rug had just been yanked out from under him.

"When that poem was written," Vittoria declared, "Raphael's tomb was somewhereelse. Back then, the Pantheon had nothing at all to do with Raphael!"

"Raphael's tomb. He wasn't buried here until 1759. A centuryafter Diagramma was published."

Langdon felt himself sway. Impossible… I was certain…

Langdon stared at her, trying to make sense of the words. "No," he replied. "Raphael died in 1520, longbefore Diagramma."

"What dates don't match?"

"He was both, of course. They all were. Michelangelo, da Vinci, Raphael."

The docent now looked like he wanted to leave. "No, ma"am. The only Santi I've ever heard of is Raphael the architect."

Vittoria took charge. "We're looking for something called Santi's earthly tomb. In Rome. Can you tell us what that might be?"

"Architect?" Vittoria said. "I thought he was a painter!"

"How aboutanyone famous at all? Maybe a scientist or a poet or an astronomer named Santi?"

"Illuminati?" The docent gasped, looking again at the document in Langdon's hand. "Whoare you people?"

"Impossible!" Langdon cursed to himself. "The Illuminati altars of science were here in Rome. I'm certain of it!"

The docent shrugged. "Not that I know of."

The docent looked unsettled. "This was Raphael's only tomb in Rome."

Langdon tried to think, but his mind refused to engage. If Raphael's tomb wasn't in Rome in 1655, then what was the poem referring to? Santi's earthly tomb with demon's hole? What the hell is it? Think!

"Was there another artist called Santi?" Vittoria asked.

Monet"sWater Lilies.

Langdon didn't know whether it was the docent's words or the ornate tombs around them that brought the revelation to mind, but it didn't matter. The thought occurred. Santi was an architect. From there the progression of thoughts fell like dominoes. Renaissance architects lived for only two reasons -- to glorify God with big churches, and to glorify dignitaries with lavish tombs. Santi's tomb. Could it be? The images came faster now…

Michelangelo"sDavid.

da Vinci"sMona Lisa.

Santi"searthly tomb…

"Santidesigned the tomb," Langdon said.

"It's not a reference to where Raphael is buried, it's referring to a tomb hedesigned."

"What are you talking about?"

"I misunderstood the clue. It's not Raphael's burial site we're looking for, it's a tomb Raphael designed for someoneelse. I can't believe I missed it. Half of the sculpting done in Renaissance and Baroque Rome was for the funeraries." Langdon smiled with the revelation. "Raphael must have designed hundreds of tombs!"

Vittoria turned. "What?"

Langdon's smile faded. "Oh."

"Are any of Raphael's tombs or chapels consideredearthly?"

Vittoria did not look happy. "Hundreds?"

Langdon felt suddenly inadequate. He knew embarrassingly little about Raphael's work. Michelangelo he could have helped with, but Raphael's work had never captivated him. Langdon could only name a couple of Raphael's more famous tombs, but he wasn't sure what they looked like.

"Any of themearthly, professor?"

The docent now looked distressed. "A tomb of Raphael's? I don't know. He designed so many. And you probably would mean achapel by Raphael, not a tomb. Architects always designed the chapels in conjunction with the tomb."

Langdon realized the man was right.

The man shrugged. "I'm sorry. I don't know what you mean. Earthly really doesn't describe anything I know of. I should be going."

Apparently sensing Langdon's stymie, Vittoria turned to the docent, who was now inching away. She grabbed his arm and reeled him in. "I need a tomb. Designed by Raphael. A tomb that could be consideredearthly."

Langdon looked up suddenly. He had momentarily forgotten the second part of the line. Demon's hole? "Yes!" he said to the docent. "That's it! Do any of Raphael's chapels have an oculus in them?"

"Not a thing."

The docent shook his head. "To my knowledge the Pantheon is unique." He paused. "But…"

Vittoria held his arm and read from the top line of the folio. "From Santi's earthly tomb with demon's hole. Does that mean anything to you?"

"But what!" Vittoria and Langdon said in unison.

"An undercroft?" Langdon asked. "As in acrypt?"

Now the docent cocked his head, stepping toward them again. "A demon's hole?" He muttered to himself and picked at his teeth. "Demon's hole… that is…buco diàvolo?"

Vittoria nodded. "Literally, yes."

The docent smiled faintly. "Now there's a term I have not heard in a while. If I'm not mistaken, abuco diàvolo refers to an undercroft."

"Yes, but a specific kind of crypt. I believe a demon's hole is an ancient term for a massive burial cavity located in a chapel… underneath another tomb."

"An ossuary annex?" Langdon demanded, immediately recognizing what the man was describing.

The docent looked impressed. "Yes! That is the term I was looking for!"

Langdon considered it. Ossuary annexes were a cheap ecclesiastic fix to an awkward dilemma. When churches honored their most distinguished members with ornate tombs inside the sanctuary, surviving family members often demanded the family be buried together… thus ensuring they too would have a coveted burial spot inside the church. However, if the church did not have space or funds to create tombs for an entire family, they sometimes dug an ossuary annex -- a hole in the floor near the tomb where they buried the less worthy family members. The hole was then covered with the Renaissance equivalent of a manhole cover. Although convenient, the ossuary annex went out of style quickly because of the stench that often wafted up into the cathedral. Demon's hole, Langdon thought. He had never heard the term. It seemed eerily fitting.

Langdon's heart was now pounding fiercely. From Santi's earthly tomb with demon's hole. There seemed to be only one question left to ask. "Did Raphael design any tombs that had one of these demon's holes?"

"Where!" Vittoria almost shouted.

"Incoherent with the architecture. Raphael was only the architect. Some other sculptor did the interior adornments. I can't remember who."

The docent scratched his head. "Actually. I'm sorry… I can only think of one."

The docent eyed them strangely. "It's called the Chigi Chapel. Tomb of Agostino Chigi and his brother, wealthy patrons of the arts and sciences."

"Sciences?"Langdon said, exchanging looks with Vittoria.

"Different?" Langdon said. "How?"

Only one? Langdon could not have dreamed of a better response.

Langdon could scarcely believe his ears. "Pyramids? The chapel contains pyramids?"

Langdon was now all ears. The anonymous Illuminati master, perhaps?

"Where?" Vittoria asked again.

"Whoever did the interior monuments lacked taste," the docent said."Dio mio! Atrocitàs! Who would want to be buried beneathpirámides?"

The docent ignored the question, seeming enthusiastic again to be of service. "As for whether or not the tomb isearthly, I don't know, but certainly it is… shall we saydifferénte."

"About a mile north. In the church of Santa Maria del Popolo."

"Santa Maria del Popolo! One mile north. Get your men over there now! We've got four minutes!"

Vittoria exhaled. "Thank you. Let's --"

Olivetti sounded bewildered. "Wrong? What do you mean?"

"No," Vittoria said, heading for the door. "Chapel of theEarth."

Vittoria grabbed the docent's arm. "Signore, where is this Chigi Chapel?"

Vittoria Vetra whipped out her cell phone as she dashed into Piazza della Rotunda. "Commander Olivetti," she said. "This is the wrong place!"

"Chapel of the Land?" Langdon asked.

He shook his head. "No, but it should have dawned on me earlier. The Chigi Chapel was not always known as the Chigi. It used to be called Capella della Terra."

"Hey," the docent said, "I just thought of something. What a fool I am."

"The first altar of science is at the Chigi Chapel!"

"I know," the docent scoffed. "Terrible, isn't it?"

"Where?" Now Olivetti sounded angry. "But Mr. Langdon said --"

Vittoria stopped short. "Please don't tell me you made a mistake."

"Move!" Vittoria snapped the phone shut.

"But my men are in positionhere! I can't possibly --"

Behind her, Langdon emerged from the Pantheon, dazed.

She grabbed his hand and pulled him toward the queue of seemingly driverless taxis waiting by the curb. She pounded on the hood of the first car in line. The sleeping driver bolted upright with a startled yelp. Vittoria yanked open the rear door and pushed Langdon inside. Then she jumped in behind him.

Looking delirious and half terrified, the driver hit the accelerator, peeling out down the street.

"Santa Maria del Popolo," she ordered."Presto!"