Langdon read the verse slowly. "An ancient word of wisdom frees this scroll… and helps us keep her scatter'd family whole… a headstone praised by templars is the key… and Atbash will reveal the truth to thee."

mirrored text Sophie quickly found some paper and copied it down longhand. When she was done, the three of them took turns reading the text. It was like some kind of archaeological crossword… a riddle thatpromised to reveal how to open the cryptex.

Fifteen thousand feet in the air, Robert Langdon felt the physical world fade away as all of his thoughts converged on Saunière's mirror-image poem, which was illuminated through the lid of the box.

Langdon had come across this meter often over the years while researching secret societies across Europe, including just last year in the Vatican Secret Archives. For centuries, iambic pentameter had been a preferred poetic meter of outspoken literati across the globe, from the ancient Greek writer Archilochus to Shakespeare, Milton, Chaucer, and Voltaire -- bold souls who chose to write their social commentaries in a meter that many of the day believed had mystical properties. The roots of iambic pentameter were deeply pagan.

Before Langdon could even ponder what ancient password the verse was trying to reveal, he felt something far more fundamental resonate within him -- the meter of the poem. Iambic pentameter.

Arranged in strings of five. Pentameter. Five for the pentacle of Venus and the sacred feminine.

"It's pentameter!" Teabing blurted, turning to Langdon. "And the verse is in English! La linguapura!" Langdon nodded. The Priory, like many European secret societies at odds with the Church, had considered English the only European pure language for centuries. Unlike French, Spanish, and Italian, which were rooted in Latin -- the tongue of the Vatican -- English was linguistically removed from Rome's propaganda machine, and therefore became a sacred, secret tongue for those brotherhoods educated enough to learn it.

"This poem," Teabing gushed, "references not only the Grail, but the Knights Templar and the scattered family of Mary Magdalene! What more could we ask for?"

Iambs. Two syllables with opposite emphasis. Stressed and unstressed. Yin yang. A balanced pair.

"The password," Sophie said, looking again at the poem. "It sounds like we need some kind of ancient word of wisdom?"

"Abracadabra?" Teabing ventured, his eyes twinkling.

"Leigh," Langdon said, "you're the Templar specialist. Any ideas?"

Teabing was silent for several seconds and then sighed. "Well, a headstone is obviously a grave marker of some sort. It's possible the poem is referencing a gravestone the Templars praised at the tomb of Magdalene, but that doesn't help us much because we have no idea where her tomb is."

"The password," Sophie said, "appears to have something to do with the Templars." She read the text aloud. "A headstone praised by Templars is the key."

A word of five letters, Langdon thought, pondering the staggering number of ancient words that might be considered words of wisdom -- selections from mystic chants, astrological prophecies, secret society inductions, Wicca incantations, Egyptian magic spells, pagan mantras -- the list was endless.

"The last line," Sophie said, "says that Atbash will reveal the truth. I've heard that word. Atbash."

"I'm not surprised," Langdon replied. "You probably heard it in Cryptology 101. The Atbash Cipher is one of the oldest codes known to man." Of course! Sophie thought. The famous Hebrew encoding system.

"The only problem," Langdon said, "is that we don't have anything on which to apply the cipher."

The Atbash Cipher had indeed been part of Sophie's early cryptology training. The cipher dated back to 500 B. C. and was now used as a classroom example of a basic rotational substitution scheme. A common form of Jewish cryptogram, the Atbash Cipher was a simple substitution codebased on the twenty-two-letter Hebrew alphabet. In Atbash, the first letter was substituted by the last letter, the second letter by the next to last letter, and so on.

Teabing sighed. "There must be a code word on the headstone. We must find this headstone praised by Templars."

"Atbash is sublimely appropriate," Teabing said. "Text encrypted with Atbash is found throughout the Kabbala, the Dead Sea Scrolls, and even the Old Testament. Jewish scholars and mystics are still finding hidden meanings using Atbash. The Priory certainly would include the Atbash Cipheras part of their teachings."

Sophie sensed from the grim look on Langdon's face that finding the Templar headstone would be no small feat.

Atbash is the key, Sophie thought. But we don't have a door.

It was three minutes later that Teabing heaved a frustrated sigh and shook his head. "My friends, I'm stymied. Let me ponder this while I get us some nibblies and check on Rémy and our guest."He stood up and headed for the back of the plane.

Outside the window, the blackness of the predawn was absolute. Sophie felt as if she were being hurtled through space with no idea where she would land. Having grown up solving her grandfather's riddles, she had the uneasy sense right now that this poem before them contained information they still had not seen.

Also plaguing her thoughts was a fear that what they eventually found inside this cryptex would not be as simple as "a map to the Holy Grail." Despite Teabing's and Langdon's confidence that the truth lay just within the marble cylinder, Sophie had solved enough of her grandfather's treasure hunts to know that Jacques Saunière did not give up his secrets easily.

Sophie felt tired as she watched him go.

There is more there, she told herself. Ingeniously hidden… but present nonetheless.