Gessner shrugged. “Your talk was entertaining, but I found your subject matter, how shall I say it…predictably metaphysical.”

  “Oh,” Katherine said. “I’m sorry to hear that.”

  “I mean no disrespect to noetics, but legitimate scientists like myself give no credence to ethereal notions like the soul, spiritual visions, or cosmic consciousness. We believe that all human experience—from religious ecstasies to debilitating fears—stem from nothing more than brain chemistry. Cause-and-effect physics. The rest is…delusion.”

  Did she just call herself legitimate and Katherine delusional? Langdon bristled, but Katherine smiled and gave his leg a playful squeeze under the table.

  “I find it curious,” Gessner continued, “that after your doctorate in neurochemistry—the most materialist of specialties—you drifted away into the oblivion of noetics.”

  “You mean California?” Katherine quipped. “I guess it made me want to see the bigger picture.”

  “I’m sorry,” Langdon interjected, unable to contain himself. “But with such a low opinion of noetic science, why did you invite Dr. Solomon to speak?”

  Gessner seemed amused by the question. “Two reasons, really. First, our original speaker—Dr. Ava Easton from the European Brain Council—had to cancel. We needed another female to fill her spot, and I figured someone like Katherine would jump at the chance. And second, I read an interview in which Katherine generously confessed that one of my articles had helped inspire part of her upcoming book.”

  “True,” Katherine said. “I wondered if you saw that.”

  “I did see it, Katherine,” Gessner said, her patronizing tone more suited to addressing a child. “Although you didn’t mention which of my articles inspired you?”

  “ ‘The Brain Chemistry of Epilepsy,’ ” Katherine replied. “European Journal of Neuroscience.”

  “A bit outside the purview of a noeticist, no? I do hope you’re not twisting my research to fit your own conclusions.”

  “Not at all,” Katherine said.

  Langdon marveled at Katherine’s politeness. More than I could muster for this woman.

  “Nonetheless,” Gessner replied, “as a professional courtesy, I’d appreciate a chance to read that section in advance. You must have a copy of your manuscript with you.”

  “Actually, I do not,” Katherine said truthfully.

  Gessner looked skeptical. “Well then, perhaps you could get one for me. If I like it, I’d consider offering you a celebrity endorsement, which could be quite helpful for your credibility with this first book.”

  “That’s very kind of you,” Katherine replied, exhibiting saintly patience. “I’ll ask my editor about that.”

  Gessner looked annoyed at being rebuffed. “As you wish, but at least let me invite you to my private lab tomorrow to show you some of my work. I think you’ll find it eye-opening. I’d love the chance to enlighten you.”

  Langdon shifted restlessly, but Katherine took his hand under the table and squeezed it with surprising strength, holding him at bay as she accepted Gessner’s invitation.

  After twenty minutes, Gessner was still talking…about what, Langdon had lost track. After half of his vile maple-and-bacon cocktail, his mouth tasted like breakfast. If Gessner’s monologue went much longer, he was definitely going to need another round.

  Perhaps a fried-egg martini?

  Katherine had only partially finished her absinthe but was already starting to show the effects, slurring her words slightly and struggling to keep her eyes open.

  “Considering the innovative nature of my research,” Gessner said offhandedly, “you’ll obviously need to sign a nondisclosure before you come to the lab tomorrow.”

  To Langdon, this seemed an obscenely self-important requirement among colleagues.

  “In fact, I have one with me now,” Gessner said, pulling out a small leather briefcase and starting to unlock it. “We can get it out of the way before tomorrow’s—”

  “Actually,” Langdon interrupted, “I wonder if Katherine’s in any state to read a legal document. Perhaps tomorrow when she arrives at your lab?”

  Clearly displeased, Gessner stared at him over her briefcase, as if weighing Langdon’s resolve. Finally, she said, “Okay, that works too.”

  As Gessner fell back into conversation with Katherine, Langdon found himself wondering why a neuroscientist who thought so little of Katherine’s work would be so eager to show off her private lab. Whatever Gessner’s motives might have been, tomorrow morning Langdon planned to suggest that Katherine gracefully opt out of the tour.

  “It’s nothing personal, Katherine!” Gessner exclaimed loudly, breaking Langdon’s train of thought. “You know I’ve never been shy about my distaste for the paranormal and PSI science. Remember my Scientific American cover?”

  “I do,” Katherine said, smiling. “Dr. Brigita Gessner, don’t call her a neuro-PSI-entist.”

  “Yes,” she said, laughing too loudly again. “Everyone got in on that joke. A fan sent me a mouse pad with my quote: ‘There’s no PSI in science.’ And a colleague even joked that I should change all my passwords to P-S-I because it was the last thing anyone would ever guess I would choose!”

  “That is funny,” Katherine said, sipping her absinthe.

  “What was even funnier was that years later, when I had to choose a security password for my new lab, I remembered his advice…and I chose PSI as my passcode!”

  Langdon raised an eyebrow, questioning which was less probable—that Gessner had used a three-letter passcode to protect her lab or that she would tell them what it was.

  “Not literally P-S-I, of course,” she added, laughing. “I encrypted it. Quite cleverly, if I do say so myself.”

  Which you just did.

  “Professor,” she said, glancing over. “I believe you’re a puzzle buff, no? You’d be impressed with my encryption.”

  “No doubt,” he managed, barely listening.

  Gessner preened. “I describe my ingenious little code as ‘an Arabic tribute to an ancient Greek with a little Latin twist.’ ” She plucked the lemon rind from the rim of her glass and let it fall dramatically into her drink. Mic drop.

  Langdon had no idea what she was talking about. “Sounds very clever.”

  “Robert could decipher it,” Katherine blurted, the absinthe’s effects on full display now. “He’s an expert with codes.”

  “I’ll take that bet,” Gessner said with a smirk. “I calculate the professor’s chances of guessing are just under one in three and a half trillion.”

  Langdon didn’t miss a beat. “Sounds like a seven-character alphanumeric.”

  Gessner recoiled, wide-eyed, startled to have been so quickly outflanked.

  Katherine let out a liquor-laced laugh. “I told you, he’s very good at codes!”

  “And exponentials, apparently,” Gessner said, clearly unsettled. “Okay, Professor, no more hints for you.”

  “And on that note,” Langdon said, standing brusquely, “I think it’s a good time to call it a night.”

  “Ah, Father says the party’s over,” Gessner said, getting to her feet, leaving most of her vodka tonic behind. “Katherine, I’ll see you in the morning. Eight a.m. sharp at Crucifix Bastion.”

  We’ll see, Langdon thought.

  As Katherine stood, she drained the remainder of her absinthe in a single swallow. Langdon calculated he now had approximately three minutes to get her upstairs before the concoction fully hit her.

  They said their goodbyes, and as Langdon helped Katherine down the hall in the direction of their suite, he chided himself for tolerating Gessner for so long tonight. He had met plenty of self-important academics, but Brigita Gessner took arrogance to an entirely new level.

  An Arabic tribute to an ancient Greek with a Latin twist? Seriously?

  Langdon wished he’d been able to decipher Gessner’s “ingenious passcode” on the spot, if only to blunt her unbearable self-importance. But the moment had passed. Forget it, he urged. Who cares?

  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—Pythagoras, Euclid, Archimedes.

  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 Janáček. 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.

  CHAPTER 25

  Images of Katherine Solomon played in The Golěm’s mind as his taxi climbed the ridge toward Crucifix Bastion. He could still see her onstage at Prague Castle…delivering her remarkable lecture. The Golěm had attended, sitting quietly in back, dressed unremarkably, as he was now.

  The Golěm felt drawn to Katherine’s ideas, sensing at times that she had been speaking directly to him. I am living proof, Katherine, that you are correct. For over an hour, Katherine had held the crowd in Vladislav Hall in rapt attention, alive with the thrill of new possibility…a fresh outlook on the workings of human consciousness.

  One moment, in particular, had spoken to him.

  “There exists an extraordinary phenomenon,” Katherine had said, “that proves beyond any shadow of a doubt that our traditional views of consciousness are entirely wrong. It’s called sudden savant syndrome, and the clinical definition is as follows: ‘The abrupt manifestation in a human mind of a unique skill or knowledge that previously was nonexistent.’ ” She smiled. “In other words, you get conked on the head and you wake up a virtuoso violinist, or fluent in Portuguese, or a genius at math—where you previously possessed none of these skills.”

  Katherine quickly ran through a series of slides and video clips of individuals who had experienced sudden savant syndrome.

  REUBEN NSEMOH—a sixteen-year-old American who was kicked in the head during a soccer game, fell into a coma, and woke up speaking perfect Spanish.

  DEREK AMATO—a middle-aged man who dove into a pool, hit his head, and woke up a musical genius and virtuoso pianist.

  ORLANDO L. SERRELL—a ten-year-old boy struck by a baseball who found he suddenly had the ability to do astonishingly complicated calendrical calculations.

  “The obvious question,” Katherine said, “is, how is this possible? How could a kick to the head magically impart into a brain the entirety of the Spanish language? Or a lifetime’s practice on the violin? Or the ability to pinpoint precise dates that are centuries in the past or future? The answer is—in our current model of the brain—all of these events are, quite literally, impossible.”

  She motioned to a young man eyeing his phone. “Sir, imagine you hurled that phone against the wall, and when you picked it up, your photo gallery contained brand-new photos…of places you’d never been.”

  “Impossible,” the man agreed.

  The Golěm understood, of course, how this could happen. He understood why cosmic signals got crossed. And clearly so did Katherine Solomon.

  “Then, of course, there’s the astonishing tale of Michael Thomas Boatwright.”

  Katherine went on to tell the story of a U.S. Navy vet who was found unconscious in a hotel room and awoke speaking fluent Swedish; he had no recollection of his own life, instead recalling his life as a Swede named Johan Ek.

  Driving her point home, she relayed the well-known story of James Leininger—a two-year-old boy haunted by nightmares of being trapped in the cockpit of a burning fighter jet. In his waking hours, young James drew pictures of a burning jet and talked through complicated preflight routines, using technical vocabulary that his parents, and most certainly the young child, had never heard. When his frightened parents asked him where he got this information, the boy declared his name was not James Leininger but rather James Huston, and he was a fighter pilot who flew off “a Natoma” with his friend Jack. To the parents’ astonishment, a search of World War II records revealed a fighter pilot named James Huston had flown off the Natoma Bay aircraft carrier with fellow pilot Jack Larsen. Huston had crashed and died, trapped in his burning cockpit. The story only got stranger from there, and it was now the subject of numerous documentaries as well as endless online speculation.