Grouard yanked his walkie-talkie off his belt and attempted to radio for backup. All he heard was static. The additional electronic security in this chamber always wrought havoc with the guards' communications. I have to move to the doorway. Still aiming his weapon at Langdon, Grouard began backing slowly toward the entrance. On his third step, he spied something that made him stop short.

What the hell is that!

Security warden Claude Grouard simmered with rage as he stood over his prostrate captive in front of the Mona Lisa. This bastard killed Jacques Saunière! Saunière had been like a well-loved father to Grouard and his security team.

An inexplicable mirage was materializing near the center of the room. A silhouette. There was someone else in the room? A woman was moving through the darkness, walking briskly toward the far left wall. In front of her, a purplish beam of light swung back and forth across the floor, as if she were searching for something with a colored flashlight.

Grouard wanted nothing more than to pull the trigger and bury a bullet in Robert Langdon's back.

As senior warden, Grouard was one of the few guards who actually carried a loaded weapon. He reminded himself, however, that killing Langdon would be a generous fate compared to the misery about to be communicated by Bezu Fache and the French prison system.

"Qui est là?" Grouard demanded, feeling his adrenaline spike for a second time in the last thirty seconds. He suddenly didn't know where to aim his gun or what direction to move.

He now recognized the purple light as ultraviolet, consistent with a PTS team, and yet he could not understand why DCPJ would be looking for evidence in here.

Police Technique et Scientifique. Grouard was sweating now. I thought all the agents were gone!

"Sophie Neveu." Somewhere in the distant recesses of Grouard's mind, the name registered. Sophie Neveu? That was the name of Saunière's granddaughter, wasn't it? She used to come in here as a little kid, but that was years ago. This couldn't possibly be her! And even if it were Sophie Neveu, that was hardly a reason to trust her; Grouard had heard the rumors of the painful falling-out between Saunière and his granddaughter.

"PTS," the woman replied calmly, still scanning the floor with her light.

"C'est mot," the voice responded in calm French.

"Votre nom!" Grouard yelled, instinct telling him something was amiss. "Répondez!"

Warden Grouard was not about to take that on faith. I need backup! Trying his walkie-talkie again, he got only static. The entrance was still a good twenty yards behind him, and Grouard began backing up slowly, choosing to leave his gun trained on the man on the floor. As Grouard inched backward, he could see the woman across the room raising her UV light and scrutinizing a large painting that hung on the far side of the Salle des Etats, directly opposite the Mona Lisa.

Grouard gasped, realizing which painting it was.

"You know me," the woman called. "And Robert Langdon did not kill my grandfather. Believe me."

What in the name of God is she doing?

Across the room, Sophie Neveu felt a cold sweat breaking across her forehead. Langdon was still spread-eagle on the floor. Hold on, Robert. Almost there. Knowing the guard would never actually shoot either of them, Sophie now turned her attention back to the matter at hand, scanning the entire area around one masterpiece in particular -- another Da Vinci. But the UV light revealed nothing out of the ordinary. Not on the floor, on the walls, or even on the canvas itself.

Grand-père, I'm here! But I don't see it!

There must be something here!

Behind her, Sophie could hear the guard trying to radio again for help.

The painting before her had no protective glass on which to write a message, and Sophie knew her grandfather would never have defaced this masterpiece by writing on the painting itself.

Sophie felt totally certain she had deciphered her grandfather's intentions correctly.

She paused. At least not on the front. Her eyes shot upward, climbing the long cables that dangled from the ceiling to support the canvas.

The masterpiece she was examining was a five-foot-tall canvas. The bizarre scene Da Vinci had painted included an awkwardly posed Virgin Mary sitting with Baby Jesus, John the Baptist, and the Angel Uriel on a perilous outcropping of rocks. When Sophie was a little girl, no trip to the Mona Lisa had been complete without her grandfather dragging her across the room to see this second painting.

Think!

She pictured the message scrawled on the protective glass of the Mona Lisa. So dark the con of man.

What else could he possibly intend?

It took only seconds to realize her instinct had been wrong. The back of the painting was pale and blank. There was no purple text here, only the mottled brown backside of aging canvas and -- Wait.

Could that be it? Grabbing the left side of the carved wood frame, she pulled it toward her. The painting was large and the backing flexed as she swung it away from the wall. Sophie slipped her head and shoulders in behind the painting and raised the black light to inspect the back.

Sophie's eyes locked on an incongruous glint of lustrous metal lodged near the bottom edge of the frame's wooden armature. The object was small, partially wedged in the slit where the canvas met the frame. A shimmering gold chain dangled off it.

To Sophie's utter amazement, the chain was affixed to a familiar gold key. The broad, sculpted head was in the shape of a cross and bore an engraved seal she had not seen since she was nine years old. A fleur-de-lis with the initials P. S. In that instant, Sophie felt the ghost of her grandfather whispering in her ear. When the time comes, the key will be yours. A tightness gripped her throat as she realized that her grandfather, even in death, had kept his promise. This key opens a box, his voice was saying, where I keep many secrets.

"Au secours!" the guard's voice yelled.

Sophie now realized that the entire purpose of tonight's word game had been this key. Her grandfather had it with him when he was killed. Not wanting it to fall into the hands of the police, he hid it behind this painting. Then he devised an ingenious treasure hunt to ensure only Sophie would find it.

Static.

Sophie snatched the key from behind the painting and slipped it deep in her pocket along with the UV penlight. Peering out from behind the canvas, she could see the guard was still trying desperately to raise someone on the walkie-talkie. He was backing toward the entrance, still aiming the gun firmly at Langdon.

"Au secours!" he shouted again into his radio.

He can't transmit, Sophie realized, recalling that tourists with cell phones often got frustrated inhere when they tried to call home to brag about seeing the Mona Lisa. The extra surveillance wiring in the walls made it virtually impossible to get a carrier unless you stepped out into the hall.

The guard was backing quickly toward the exit now, and Sophie knew she had to act immediately.

Gazing up at the large painting behind which she was partially ensconced, Sophie realized that Leonardo da Vinci, for the second time tonight, was there to help.

Another few meters, Grouard told himself, keeping his gun leveled.

"Arrêtez! Ou je la détruis!" the woman's voice echoed across the room.

Grouard glanced over and stopped in his tracks. "Mon dieu, non!"

What is she doing!

The canvas started to bulge in the middle, the fragile outlines of the Virgin Mary, Baby Jesus, and John the Baptist beginning to distort.

When he saw it, his blood went cold.

"Non!" Grouard screamed, frozen in horror as he watched the priceless Da Vinci stretching. The woman was pushing her knee into the center of the canvas from behind!

Through the reddish haze, he could see that the woman had actually lifted the large painting off its cables and propped it on the floor in front of her. At five feet tall, the canvas almost entirely hid her body. Grouard's first thought was to wonder why the painting's trip wires hadn't set off alarms, but of course the artwork cable sensors had yet to be reset tonight.

"NON!" Grouard wheeled and aimed his gun at her but instantly realized it was an empty threat. The canvas was only fabric, but it was utterly impenetrable -- a six-million-dollar piece of body armor.

Moments later, Langdon's pulse was still thundering as he ran beside Sophie down the emergency stairwell toward the ground level. Neither of them had said a word since leaving the trembling Louvre guard lying in the Salle des Etats. The guard's pistol was now clutched tightly in Langdon's hands, and he couldn't wait to get rid of it. The weapon felt heavy and dangerously foreign.

"Set down your gun and radio," the woman said in calm French, "or I'll put my knee through this painting. I think you know how my grandfather would feel about that." Grouard felt dizzy. "Please… no. That's Madonna of the Rocks!" He dropped his gun and radio, raising his hands over his head.

I can't put a bullet through a Da Vinci!

"Thank you," the woman said. "Now do exactly as I tell you, and everything will work out fine."

Taking the stairs two at a time, Langdon wondered if Sophie had any idea how valuable a painting she had almost ruined. Her choice in art seemed eerily pertinent to tonight's adventure. The Da Vinci she had grabbed, much like the Mona Lisa, was notorious among art historians for its plethora of hidden pagan symbolism.

"Madonna of the Rocks," she replied. "But I didn't choose it, my grandfather did. He left me a little something behind the painting."

"You chose a valuable hostage," he said as they ran.

Langdon shot her a startled look. "What!? But how did you know which painting? Why Madonna of the Rocks?"

"So dark the con of man." She flashed a triumphant smile. "I missed the first two anagrams, Robert. I wasn't about to miss the third."