More than three thousand people are entombed or enshrined within Westminster Abbey. The colossal stone interior burgeons with the remains of kings, statesmen, scientists, poets, and musicians. Their tombs, packed into every last niche and alcove, range in grandeur from the most regal of mausoleums -- that of Queen Elizabeth I, whose canopied sarcophagus inhabits its own private, apsidal chapel -- down to the most modest etched floor tiles whose inscriptions have worn away with centuries of foot traffic, leaving it to one's imagination whose relics might lie below the tile in the undercroft.

Designed in the style of the great cathedrals of Amiens, Chartres, and Canterbury, Westminster Abbey is considered neither cathedral nor parish church. It bears the classification of royal peculiar, subject only to the Sovereign. Since hosting the coronation of William the Conqueror on Christmas Day in 1066, the dazzling sanctuary has witnessed an endless procession of royal ceremonies and affairs of state -- from the canonization of Edward the Confessor, to the marriage of Prince Andrew and Sarah Ferguson, to the funerals of Henry V, Queen Elizabeth I, and Lady Diana.

Hurrying through the grand portico on the north transept, Langdon and Sophie were met by guards who politely ushered them through the abbey's newest addition -- a large walk-through metal detector -- now present in most historic buildings in London. They both passed through without setting off the alarm and continued to the abbey entrance.

Stepping across the threshold into Westminster Abbey, Langdon felt the outside world evaporate with a sudden hush. No rumble of traffic. No hiss of rain. Just a deafening silence, which seemed to reverberate back and forth as if the building were whispering to itself.

Even so, Robert Langdon currently felt no interest in any of the abbey's ancient history, save one event -- the funeral of the British knight Sir Isaac Newton.

Langdon's and Sophie's eyes, like those of almost every visitor, shifted immediately skyward, where the abbey's great abyss seemed to explode overhead. Gray stone columns ascended like redwoods into the shadows, arching gracefully over dizzying expanses, and then shooting back down to the stone floor. Before them, the wide alley of the north transept stretched out like a deep canyon, flanked by sheer cliffs of stained glass. On sunny days, the abbey floor was a prismatic patchwork of light. Today, the rain and darkness gave this massive hollow a wraith like aura… more like that of the crypt it truly was.

In London lies a knight a Pope interred.

"It's practically empty," Sophie whispered.

Langdon felt disappointed. He had hoped for a lot more people. A more public place. Their earlier experience in the deserted Temple Church was not one Langdon wanted to repeat. He had been anticipating a certain feeling of security in the popular tourist destination, but Langdon's recollections of bustling throngs in a well-lit abbey had been formed during the peak summer tourist season. Today was a rainy April morning. Rather than crowds and shimmering stained glass, all Langdon saw was acres of desolate floor and shadowy, empty alcoves.

"We passed through metal detectors," Sophie reminded, apparently sensing Langdon's apprehension. "If anyone is in here, they can't be armed."

Langdon nodded but still felt circumspect. He had wanted to bring the London police with them, but Sophie's fears of who might be involved put a damper on any contact with the authorities. We need to recover the cryptex, Sophie had insisted. It is the key to everything.

She was right, of course.

Unfortunately, their only chance to recover the keystone seemed to be here and now… at the tomb of Isaac Newton. Whoever held the cryptex would have to pay a visit to the tomb to decipher the final clue, and if they had not already come and gone, Sophie and Langdon intended to intercept them.

The key to finding the Holy Grail.

The key to getting Leigh back alive.

Striding toward the left wall to get out of the open, they moved into an obscure side aisle behind a row of pilasters. Langdon couldn't shake the image of Leigh Teabing being held captive, probably tied up in the back of his own limousine. Whoever had ordered the top Priory members killed would not hesitate to eliminate others who stood in the way. It seemed a cruel irony that Teabing -- a modern British knight -- was a hostage in the search for his own countryman, Sir Isaac Newton.

"Which way is it?" Sophie asked, looking around.

Langdon knew better than to wander aimlessly in here. Westminster Abbey was a tangled warren of mausoleums, perimeter chambers, and walk-in burial niches. Like the Louvre's Grand Gallery, it had a lone point of entry -- the door through which they had just passed -- easy to find your way in, but impossible to find your way out. A literal tourist trap, one of Langdon's befuddled colleagues had called it. Keeping architectural tradition, the abbey was laid out in the shape of a giant crucifix. Unlike most churches, however, it had its entrance on the side, rather than the standard rear of the church via the narthex at the bottom of the nave. Moreover, the abbey had a series of sprawling cloisters attached. One false step through the wrong archway, and a visitor was lost in a labyrinth of outdoor passageways surrounded by high walls.

The tomb. Langdon had no idea. "We should find a docent and ask."

The key to learning who is behind this.

"Docents wear crimson robes," Langdon said, approaching the center of the church. Peering obliquely across the towering gilded altar to the far end of the south transept, Langdon saw several people crawling on their hands and knees. This prostrate pilgrimage was a common occurrence in Poets' Corner, although it was far less holy than it appeared. Tourists doing grave rubbings.

"I don't see any docents," Sophie said. "Maybe we can find the tomb on our own?"

At that moment, a hundred yards down the nave, out of sight behind the choir screen, the stately tomb of Sir Isaac Newton had a lone visitor. The Teacher had been scrutinizing the monument for ten minutes now.

Newton's tomb consisted of a massive black-marble sarcophagus on which reclined the sculpted form of Sir Isaac Newton, wearing classical costume, and leaning proudly against a stack of his own books -- Divinity, Chronology, Opticks, and Philosophiae Naturalis Principia Mathematica. At Newton's feet stood two winged boys holding a scroll. Behind Newton's recumbent body rose an austere pyramid. Although the pyramid itself seemed an oddity, it was the giant shape mounted halfway up the pyramid that most intrigued the Teacher.

Without a word, Langdon led her another few steps to the center of the abbey and pointed to the right.

Sophie drew a startled breath as she looked down the length of the abbey's nave, the full magnitude of the building now visible. "Aah," she said. "Let's find a docent."

Countless orbs.

The Teacher had been convinced that once he found the tomb, discerning the missing orb would be easy. Now he was not so sure. He was gazing at a complicated map of the heavens. Was there a missing planet? Had some astronomical orb been omitted from a constellation? He had no idea. Even so, the Teacher could not help but suspect that the solution would be ingeniously clean and simple --"a knight a pope interred."

An orb.

The Teacher pondered Saunière's beguiling riddle. "You seek the orb that ought be on his tomb."

The massive orb protruding from the face of the pyramid was carved in basso-relievo and depicted all kinds of heavenly bodies -- constellations, signs of the zodiac, comets, stars, and planets. Above it, the image of the Goddess of Astronomy beneath a field of stars.

It speaks of Rosy flesh and seeded womb.

What orb am I looking for? Certainly, an advanced knowledge of astrophysics was not a prerequisite for finding the Holy Grail, was it?

The Teacher's concentration was broken by several approaching tourists. He slipped the cryptex back in his pocket and watched warily as the visitors went to a nearby table, left a donation in the cup, and restocked on the complimentary grave-rubbing supplies set out by the abbey. Armed with fresh charcoal pencils and large sheets of heavy paper, they headed off toward the front of the abbey, probably to the popular Poets' Corner to pay their respects to Chaucer, Tennyson, and Dickens by rubbing furiously on their graves.

What orb ought to be here… and yet is missing? He touched the cryptex in his pocket as if he could somehow divine the answer from Saunière's crafted marble. Only five letters separate me from the Grail.

Pacing now near the corner of the choir screen, he took a deep breath and glanced up the long nave toward the main altar in the distance. His gaze dropped from the gilded altar down to the bright crimson robe of an abbey docent who was being waved over by two very familiar individuals.

Alone again, he stepped closer to the tomb, scanning it from bottom to top. He began with the clawed feet beneath the sarcophagus, moved upward past Newton, past his books on science, past the two boys with their mathematical scroll, up the face of the pyramid to the giant orb with its constellations, and finally up to the niche's star-filled canopy.

Langdon and Neveu.

Calmly, the Teacher moved two steps back behind the choir screen. That was fast. He had anticipated Langdon and Sophie would eventually decipher the poem's meaning and come to Newton's tomb, but this was sooner than he had imagined. Taking a deep breath, the Teacher considered his options. He had grown accustomed to dealing with surprises.

Reaching down to his pocket, he touched the second object that gave him his confidence: the Medusa revolver. As expected, the abbey's metal detectors had blared as the Teacher passed through with the concealed gun. Also as expected, the guards had backed off at once when the Teacher glared indignantly and flashed his identification card. Official rank always commanded the proper respect.

I am holding the cryptex.

The only question now… what to use as bait?

Although initially the Teacher had hoped to solve the cryptex alone and avoid any further complications, he now sensed that the arrival of Langdon and Neveu was actually a welcome development. Considering the lack of success he was having with the "orb" reference, he might be able to use their expertise. After all, if Langdon had deciphered the poem to find the tomb, there was a reasonable chance he also knew something about the orb. And if Langdon knew the password, then it was just a matter of applying the right pressure.

Not here, of course.

Somewhere private.

The Teacher recalled a small announcement sign he had seen on his way into the abbey. Immediately he knew the perfect place to lure them.