13-3-2-21-1-1-8-5 Grand-père wrote his account number on the Louvre floor!

"He was the master of double-entendres," Sophie said, turning to Langdon. "He loved anything with multiple layers of meaning. Codes within codes." Langdon was already moving toward the electronic podium near the conveyor belt. Sophie grabbed the computer printout and followed.

"Ten digits," Sophie said, her cryptologic senses tingling as she studied the printout.

When Sophie had first seen the scrambled Fibonacci sequence on the parquet, she had assumed its sole purpose was to encourage DCPJ to call in their cryptographers and get Sophie involved. Later, she realized the numbers were also a clue as to how to decipher the other lines -- a sequence out of order… a numeric anagram. Now, utterly amazed, she saw the numbers had a more important meaning still. They were almost certainly the final key to opening her grandfather's mysterious safe-deposit box.

The podium had a keypad similar to that of a bank ATM terminal. The screen displayed the bank's cruciform logo. Beside the keypad was a triangular hole. Sophie wasted no time inserting the shaft of her key into the hole.

ACCOUNT NUMBER: _ _ _ _ _ _ _ _ _ _ The cursor blinked. Waiting.

The screen refreshed instantly.

Ten digits. Sophie read the numbers off the printout, and Langdon typed them in.

ACCOUNT NUMBER: 1332211185 When he had typed the last digit, the screen refreshed again. A message in several languages appeared. English was on top.

CAUTION: Before you strike the enter key, please check the accuracy of your account number.

For your own security, if the computer does not recognize your account number, this system will automatically shut down.

"Fonction terminer," Sophie said, frowning. "Looks like we only get one try." Standard ATM machines allowed users three attempts to type a PIN before confiscating their bank card. This was obviously no ordinary cash machine.

"The number looks right," Langdon confirmed, carefully checking what they had typed and comparing it to the printout.

He motioned to the ENTER key. "Fire away."

Sophie extended her index finger toward the keypad, but hesitated, an odd thought now hitting her.

"It's too random."

"Too random?" Langdon could not have disagreed more. Every bank advised its customers to choose PINs at random so nobody could guess them. Certainly clients here would be advised to choose their account numbers at random.

"Go ahead," Langdon urged. "Vernet will be back soon."

"No." She pulled her hand away. "This isn't the right account number."

"Of course it is! Ten digits. What else would it be?"

"It's far too coincidental that this supposedly random account number could be rearranged to form the Fibonacci sequence."

Langdon realized she had a point. Earlier, Sophie had rearranged this account number into the Fibonacci sequence. What were the odds of being able to do that?

Sophie was at the keypad again, entering a different number, as if from memory. "Moreover, with my grandfather's love of symbolism and codes, it seems to follow that he would have chosen an account number that had meaning to him, something he could easily remember." She finished typing the entry and gave a sly smile. "Something that appeared random… but was not."

Sophie deleted everything she had just typed in and looked up at Langdon, her gaze self-assured.

ACCOUNT NUMBER: 1123581321It took him an instant, but when Langdon spotted it, he knew she was right.

The Fibonacci sequence. 1-1-2-3-5-8-13-21 When the Fibonacci sequence was melded into a single ten-digit number, it became virtually unrecognizable. Easy to remember, and yet seemingly random. A brilliant ten-digit code that Saunière would never forget. Furthermore, it perfectly explained why the scrambled numbers on the Louvre floor could be rearranged to form the famous progression.

Langdon looked at the screen.

Whirring to a stop over the correct spot on the floor, the claw dropped down, an electric eye confirming the bar code on the box.

Sophie reached down and pressed the ENTER key.

Nothing happened.

At that moment, beneath them, in the bank's cavernous subterranean vault, a robotic claw sprang to life. Sliding on a double-axis transport system attached to the ceiling, the claw headed off in search of the proper coordinates. On the cement floor below, hundreds of identical plastic crates lay aligned on an enormous grid… like rows of small coffins in an underground crypt.

At least nothing they could detect.

Gently now, the retrieval arm set down the crate and retracted.

Then, with computer precision, the claw grasped the heavy handle and hoisted the crate vertically. New gears engaged, and the claw transported the box to the far side of the vault, coming to a stop over a stationary conveyor belt.

Upstairs, Sophie and Langdon exhaled in relief to see the conveyor belt move. Standing beside the belt, they felt like weary travelers at baggage claim awaiting a mysterious piece of luggage whose contents were unknown.

Once the arm was clear, the conveyor belt whirred to life…

The metal door slid up, and a huge plastic box appeared, emerging from the depths on the inclined conveyor belt. The box was black, heavy molded plastic, and far larger than she imagined. It looked like an air-freight pet transport crate without any air holes.

The conveyor belt entered the room on their right through a narrow slit beneath a retractable door.

The box coasted to a stop directly in front of them.

Langdon and Sophie stood there, silent, staring at the mysterious container.

Wasting no time, Sophie unhooked the two buckles facing her. Then she glanced over at Langdon.

Like everything else about this bank, this crate was industrial -- metal clasps, a bar code sticker on top, and molded heavy-duty handle. Sophie thought it looked like a giant toolbox.

Together, they raised the heavy lid and let it fall back.

At first glance, Sophie thought the crate was empty. Then she saw something. Sitting at the bottom of the crate. A lone item.

She carried it gingerly to a large receiving table and set it down. Langdon stood beside her, both of them staring at the small treasure chest her grandfather apparently had sent them to retrieve.

Stepping forward, they peered down into the crate.

The polished wooden box was about the size of a shoe box and had ornate hinges. The wood was a lustrous deep purple with a strong grain. Rosewood, Sophie realized. Her grandfather's favorite.

My God, it's heavy!

The lid bore a beautiful inlaid design of a rose. She and Langdon exchanged puzzled looks. Sophie leaned in and grabbed the box, lifting it out.

"It's a perfect size," Sophie whispered, "to hold… a chalice." It can't be a chalice.

Sophie pulled the box toward her across the table, preparing to open it. As she moved it, though, something unexpected happened. The box let out an odd gurgling sound.

Langdon stared in wonderment at the lid's hand-carved inlay -- a five-petal rose. He had seen this type of rose many times. "The five-petal rose," he whispered, "is a Priory symbol for the Holy Grail."

Sophie turned and looked at him. Langdon could see what she was thinking, and he was thinking it too. The dimensions of the box, the apparent weight of its contents, and a Priory symbol for the Grail all seemed to imply one unfathomable conclusion. The Cup of Christ is in this wooden box.

Sophie looked equally confused. "Did you just hear…?"

Langdon again told himself it was impossible.

Langdon did a double take. There's liquid inside?

The object inside was unlike anything Langdon had ever seen. One thing was immediately clear to both of them, however. This was definitely not the Cup of Christ.

Langdon nodded, lost. "Liquid."

Reaching forward, Sophie slowly unhooked the clasp and raised the lid.