Page 27 of The Secret of Secrets (Robert Langdon #6)

When they entered their suite, Katherine disappeared into the bathroom to get ready for bed.

Langdon paced the living room, knowing he was too wound up to go to sleep.

As much as he wanted to forget his encounter with Gessner, his irritation over her smug superiority had awoken his competitive spirit.

His analytical mind was already churning, looking for a way to unpack Gessner’s riddle.

Isolate each piece, he thought. An Arabic tribute…

Langdon knew there were no Arabic letters in an alphanumeric alphabet, so he was fairly certain Gessner was referring to the other Arabic alphabet—numbers—the mathematical language popularized by the Arabs over a thousand years ago.

Gessner’s passcode must be a number.

“An Arabic tribute…” he puzzled aloud, “to an ancient Greek.”

Logically, if Gessner’s passcode was a number, then her “tribute” would be numerical, so it therefore followed that the ancient Greek in question was probably associated with mathematics.

The three most famous mathematicians of ancient times were all Greeks.

Their names had been emblazoned in Langdon’s brain after his prep school math teacher Mr. Brown informed the class that their school’s ubiquitous acronym, “PEA,” was not an abbreviation for Phillips Exeter Academy as everyone believed, but rather a secret tribute to the three titans of early mathematics— P ythagoras, E uclid, A rchimedes.

So, which one might Gessner be referencing? Langdon worked his way through the list.

Pythagoras : Pythagorean theorem, theory of proportions, sphericity of the earth.

Euclid : Father of geometry, conic sections, number theory.

Archimedes : Archimedean spirals, the number pi, areas of circles.

Langdon paused.

“Pi,” he declared loudly.

Katherine called from the other room. “That’s a great idea! Call room service. I’ll have a piece too!”

Different pie, he thought, chuckling as he went into the bedroom and helped Katherine woozily into bed.

After kissing her good night, he stepped back into the living room, extracted a piece of paper and a pen from the rolltop desk, and sat down on the couch, overtaken now by a compulsive desire to finish what he had started.

The solution to Gessner’s puzzle was far from clear, but Langdon had just realized that the spelling of pi—arguably the most famous number in history—was intriguingly close to that of PSI.

Gessner said her passcode was PSI…encrypted.

Langdon sensed he was on the right track.

3.14159, he thought, jotting down pi’s most common form.

The number pi could certainly be described as a tribute to an ancient Greek, and it also was expressed in Arabic numerals, which meant it satisfied two of Gessner’s three requirements.

An Arabic tribute to an ancient Greek.

Unfortunately, the decimal point in 3.14159 was problematic. First, there were no decimal points in a pure alphanumeric passcode. And second, the decimal point was not an Arabic creation; it was invented by a Scottish mathematician, John Napier.

You can solve both problems simply by deleting the decimal point.

There was only one problem: the number 314159 represented pi…not PSI.

And it’s still missing the “little Latin twist.”

Ten minutes later, Langdon had made no further progress, and he decided he too should probably call it a night. Gessner’s passcode can wait…or better yet, be forgotten.

Langdon climbed into bed beside Katherine, where he slept soundly for several hours…until she woke up screaming from her nightmare.

A lifetime ago, Langdon thought, now standing in the darkened elevator alcove, staring at the numeric keypad and wishing he’d solved Gessner’s annoying little riddle.

On the other side of the wall, Pavel cursed loudly, and Langdon heard him dash out of the atrium, probably to go find Janá?ek. Langdon knew this moment might be an opportunity to slip out of the bastion unseen…but to where?

I’m not leaving without Katherine, he thought, increasingly fearful that something might have happened to her. I need to get downstairs.

He looked back at the keypad, wondering if he might have a better chance of deciphering the final piece of Gessner’s passcode now that an evening had passed. After all, there was a reason we “slept on” our problems; the subconscious mind could make remarkable connections while we slept.

Langdon had gone to bed last night thinking the number 314159 was an accurate representation of “an Arabic tribute to an ancient Greek.”

Still, it was not quite right.

I’m missing the Latin twist.

Langdon knew the majority of languages in the world—including English—used the lettering system known as the Roman or Latin alphabet. As he surveyed the numbers and letters on the buttons of the keypad, he realized he had become so focused on numbers that he’d forgotten he could also use letters.

Is the “Latin twist” a letter?

As he considered it, the simplest of shapes materialized in his mind—the twisting curve of the letter S .

My God, he realized. A literal “Latin twist”!

In that moment, he flashed on Gessner smugly dropping her lemon twist into the center of her drink, and he couldn’t help but be a little impressed.

“S” is the missing piece of the puzzle.

The rest was simple.

PI becomes PSI!

Gessner’s code was a mixture of Arabic and Latin symbols—numbers and letters—and if Langdon was not mistaken, the solution had to be 314S159!

He rechecked the logic against what Gessner had said. “An Arabic tribute to an ancient Greek with a Latin twist.”

The number 314159 is a purely Arabic tribute…to the Greek number pi…and the “S” in the middle is a Latin twist that turns PI…into PSI…which Gessner said was her passcode.

If there had ever been a moment to shout Archimedes’s exclamation “Eureka!” this was it, but instead Langdon moved silently to the keypad.

Holding his breath, he carefully entered seven characters into the digital screen.

3 1 4 S 1 5 9

After double-checking the sequence, he exhaled and pressed Enter.

Nothing happened.

An immediate rush of despair washed over him, but a moment later Langdon heard a click and a faint mechanical whir behind the door. The sound grew louder…an elevator ascending.

Eureka… he thought, permitting himself a relieved smile. One in 3.5 trillion.

The elevator door slid open to reveal an oversized, wood-paneled cabin. Ignoring his claustrophobia, Langdon stepped inside and searched the walls for the button that would take him down to the lab.

But this elevator had no buttons or controls of any kind.

Instead, the doors closed automatically, and Langdon felt himself descending.