Langdon suddenly realized where Katherine was headed with this. Epileptic seizures were described as a peaceful “untethering” from the physical body—in effect, a brief period of nonlocal consciousness.

  “Out-of-body experiences,” Katherine continued, “are something epileptics experience quite naturally. The epileptic brain is already wired for OBEs…meaning an epileptic would be far more likely to be a skilled remote viewer.”

  “You can’t really believe Sasha Vesna is a psychic spy for the CIA…”

  “Why not?”

  “Because I spent time with her. She has a Krazy Kitten key ring! She’s a lost, gentle soul.”

  “Gentle?!” Katherine challenged. “You said she smashed a guy in the head with a fire extinguisher!”

  “Technically that’s true…but it was to protect—”

  “Robert, I’ll admit maybe Sasha is not a remote viewer herself, but Gessner could have been studying epileptic brains to find out what makes them so prone to out-of-body experiences. Tapping into detailed neurological information about an epileptic brain could be incredibly valuable for a program trying to detach mind and body.”

  An interesting idea, Langdon thought, particularly in light of something Sasha had shared earlier today. “I forgot to mention that Gessner brought another epilepsy patient to Prague from that same institution—before Sasha—a Russian named Dmitri. He received the same surgery as Sasha and was also cured.”

  “I would say that’s significant,” Katherine said. “It’s hard to believe that Brigita Gessner was plucking epileptics from mental hospitals and curing them at her own expense, purely out of goodwill.”

  Langdon had to agree it seemed out of character. Moreover, he now realized that a test subject taken from Russia—probably with the help of the CIA—would be entirely off the radar in Europe. A ghost in Prague.

  “Let’s assume for a moment,” Katherine said, “that Gessner recruited these epileptics as study subjects for Threshold. That would explain why she was keeping Sasha around.”

  “To monitor her.”

  “Yes. Give her a minor job, an apartment, some money. Easy.”

  “I suppose…”

  “And Dmitri?” Katherine asked as they neared Folimanka Park. “Where is he now—still in Prague?”

  “Sasha said he went home to Russia after Gessner cured him.”

  “I doubt it. Maybe that’s what Gessner told Sasha, but if the CIA pulled a test subject from an institution, invested in him, made him a research subject in a top secret program…would they really just let him go home? To Russia?”

  Good point, Langdon thought, accelerating along the stretch of road before them. He craned his neck slightly to look farther down the street.

  With luck we’ll have our answers soon.

  The entrance to Threshold was just ahead.

  CHAPTER 88

  Outside the U.S. embassy, Sergeant Kerble stood on the sidewalk, freezing in his dress blues as he scanned the street for an approaching vehicle. When he finally spotted the ambassador, he was startled to see her only ten yards away.

  She’s on foot?! Alone?!

  “I know, Scott, I’m sorry,” she said, arriving and rushing past him. “I just needed some air.”

  “Where’s your vehicle?!”

  “Everything’s fine. Really. Follow me.”

  Kerble had been Ambassador Nagel’s lead security detail for two years now, and he had never known her to be careless or difficult—or erratic. The death of Michael Harris had clearly shaken her deeply.

  After climbing the stairs to the ambassador’s office, Kerble waited as Nagel dumped her coat, grabbed a bottle of water, and then, to his surprise, began typing on her computer, meticulously consulting a paper she had extracted from her coat pocket. Finally, the computer swooshed with an outbound email.

  Your attaché is dead, and you’re sending an email?

  “Okay, Scott,” she said, turning her full attention to him. “I trust the envelope’s clean?”

  “Full scan,” he assured her, having already run it through the embassy’s safety protocol for incoming mail. “No foreign substances.” He extracted the envelope from his breast pocket and laid it in front of her.

  Nagel picked it up. “A basket of kittens?”

  “Ma’am?”

  “The killer wrote to me on kitten stationery?!” She pointed to the logo of a basket of kittens on the envelope.

  “Yes, ma’am. He took the stationery from Ms. Vesna’s apartment. She seems to like cats.”

  Nagel grabbed her letter opener and carefully ran the blade under the envelope’s seam. Then she pulled out a sheet of matching stationery, which had been folded once.

  Sergeant Kerble couldn’t see what the letter said, nor could he read the ambassador’s reaction, but the message was apparently short.

  Moments after laying eyes on the letter, she laid it facedown on her desk and walked to the window. After ten full seconds of silence, she turned and faced Kerble.

  “Thank you. I’m going to need some privacy.”

  CHAPTER 89

  The entrance to the Folimanka Shelter’s “renovation project” was precisely where Ambassador Nagel had said it would be—discreetly situated in an industrial section of the city, bordered by commuter train tracks, a busy street, and the southwestern corner of Folimanka Park.

  Surrounded by a metal fence, the small triangle of land on which the entrance sat was known as Ostrčilovo Square. The triangular “square” had served many purposes over the years—a failed playground, a makeshift skate park, and, most recently, a recycling drop-off center. For the past few years, however, it had served as the Army Corps of Engineers’ staging ground for a “refurbishment” of Folimanka’s failing 1950s bomb shelter.

  Katherine felt rising nerves as Langdon drove alongside the high barricade—a solid, eight-foot wall on which signage warned:

  VSTUP ZAKÁZÁN / ZUTRITT VERBOTEN / ENTRY FORBIDDEN

  At the end of the wall, Langdon turned left and drove slowly along the second leg of the triangle, where a large informational placard had been erected with diagrams and text outlining what was happening within the walls:

  PROJEKT OBNOVY PARKU FOLIMANKA / FOLIMANKA PARK RECOVERY PROJECT

  A fortified access gate along the wall was closed, with only a small section of the gate panel affording a view of what lay beyond. Two soldiers in black fatigues were patrolling a freshly paved access road that descended into a wide, arched tunnel that disappeared beneath Folimanka Park. The mouth of the tunnel was blocked by retractable steel bollards.

  “That’s some robust security for a restoration project,” Langdon said, craning his neck as they drove by.

  A secret government project…hiding in plain sight.

  Katherine stole a final glance at the entry tunnel as they passed it. Other than the nondescript guards outside the entrance, she saw no trucks, no personnel, nothing. It seemed the ambassador might have been correct that Threshold was currently inactive.

  Langdon turned left and drove along the third and final leg of the enclosure, which ran parallel with the western edge of Folimanka Park.

  Here we go, Katherine thought, still marveling at the remarkable entry plan that Langdon had outlined earlier. His plan was rooted in a single, startling idea.

  Threshold has a secret entrance.

  Using an irrefutable chain of logic, Langdon had convinced the ambassador that the “construction entrance” on the western tip of Folimanka Park, which would serve as the main entrance when the project was complete, was not the only way in.

  Threshold had a second access point…ingeniously disguised.

  More importantly, Langdon had determined exactly where it was located…as well as how to get in.

  The Golěm stood alone in a chamber unlike any he had ever seen or imagined. Having followed the detailed directions he had forced Gessner to provide last night, his journey had finally delivered him to this surreal place.

  Threshold.

  Gessner had confessed all the details…and yet seeing it in person now left him disoriented, almost nauseous.

  They built this room with Sasha’s blood.

  Sasha had not been the project’s first victim…nor would she have been its last.

  And for that reason, Threshold will end today.

  The Golěm’s long road to this moment of retribution had taken a severe toll, and he could feel deep emotion welling up within him. He could also feel a faint but unmistakable tingling within his body—an advance warning.

  A hazy fog began to settle in the room.

  The Ether was gathering.

  “Ne seychas,” he whispered. Not now.

  Instinctively, The Golěm slid his hand into his cloak pocket to retrieve his metal wand.

  CHAPTER 90

  Jonas Faukman scowled at ChatGPT’s latest search results.

  Despite using varied prompts and approaches, his efforts to find any link between Katherine’s work and In-Q-Tel’s investments had turned up nothing but far-flung offerings that felt more like a disjointed game of Mad Libs than anything intelligent—artificial or otherwise.

  Frustrated, he abandoned his computer and walked to the window, gazing north up Broadway toward Central Park. In the dawn light, on the horizon line behind the “pencil towers” on Billionaires’ Row, storm clouds were gathering.

  He stood a while, lost in thought, and finally returned to his computer to continue his search. As he took his seat, he noticed he had a new email.

  The subject line startled and excited him.

  A MESSAGE FROM ROBERT LANGDON

  Faukman had been waiting over an hour for a phone call and was feeling increasingly anxious that something had gone wrong at the ambassador’s residence. The relief he felt seeing the email, however, was short-lived. Despite the subject line, Faukman now saw that the sender’s address was that of U.S. Ambassador Heide Nagel…the former CIA general counsel.

  She’s sending a message for him?

  Faukman could think of nobody in Prague he trusted less at the moment. If Robert was truly safe, then the ambassador should simply have let him call.

  Until I hear Robert’s voice, I won’t believe a word of this email.

  He debated whether to open the message, envisioning a virus or yet another hack, but at this point he figured he had nothing left to lose. Warily, he clicked open the message, puzzled to see what appeared to be a meaningless string of letters.

  ROT13EY&XFETHQ

  It took him a moment to realize that the first five characters did indeed have meaning. ROT13 was the name of a rotational cipher in which every letter was substituted for the letter occurring thirteen places away from it in the alphabet. Faukman knew this only because several years ago, while editing a book on ancient encryption techniques, the book’s author had regularly sent him texts playfully encrypted with ROT13.

  That author had been Robert Langdon.

  With a swell of optimism, Faukman grabbed a pencil and applied the simple decryption scheme. Then he examined the result.

  RL&KSRGUD

  His confusion lasted only a moment before he laughed out loud, half from amusement and half from relief.

  Only Robert could have written this message.

  Langdon and Faukman often commiserated over the decline of written language due to the proliferation of “textese” emoticons and abbreviations. The trend was so distressing to Faukman that he’d written a piece about it for The New Yorker, including one particularly overwrought sentence that Langdon mocked mercilessly.

  Faukman had written: To save a single keystroke by typing “gud” instead of “good” is not only indecorous, it is an abomination of indolence.

  Still chuckling over Langdon’s message, Faukman was tempted to reply: Your message is not only adroit, it brings propitious consolation.

  CHAPTER 91

  Langdon pulled the SUV to a stop and set the emergency brake. He gathered himself before climbing out of the vehicle with Katherine, well aware that he would know momentarily if his plan would lead them to success—or disaster.

  The wind on the high ridge had picked up, rustling through the woods beneath them. Langdon paused a moment. He gazed down at the snow-covered expanse that lay beyond the trees—Folimanka Park—which stretched eastward away from the ridgeline. This entire place feels different now, he thought, turning his attention to the building before them.

  Crucifix Bastion looked ghostly. The structure stood as a stark silhouette against the darkening afternoon sky. As he strode with Katherine toward the main entrance, Langdon felt a shadow of uncertainty, and he quickly reminded himself what had led him back here.

  Rational logic.

  The truth had dawned on him at the abandoned swimming pool in the ambassadorial residence. The ambassador had torn up the NDAs, called Finch on speakerphone, and convincingly lied that Finch’s wishes had been carried out. Then, to Langdon’s surprise, Finch had ordered Nagel to send a Marine security detail up to Crucifix Bastion to secure the perimeter. Finch’s priority is to secure an isolated Czech lab? Why?

  As Langdon considered it, a second thought occurred. Earlier today, Janáček had told Langdon that Prague’s surveillance system could not confirm that Katherine had arrived at the bastion, because—much to the captain’s chagrin—the all-seeing camera system appeared to be hampered by an unprecedented blind spot that blacked out the area around Gessner’s lab.

  Prague’s camera system is the Echelon surveillance network…run by the CIA.

  Now the wheels were turning, and Langdon found himself questioning the statistical improbability of Gessner’s private lab being perched on a ridge directly overlooking Threshold—the secret project that employed her.

  Unless they’re somehow connected…

  The rationale for hiding a covert intelligence facility beneath Folimanka Park made sense to Langdon—natural camouflage, access to supplies, existing infrastructure—and yet he was having trouble accepting that Threshold was built with a sole access point…only one way in or out. The design would be a death trap in a fire or emergency, which seemed an incongruous risk for an agency built on strategy, contingency, and planning ahead.

  Even the Vatican has secret escape routes!

  It was then that the ambassador revealed an unexpected twist: The entity that had quietly acquired the bastion on behalf of Gessner was none other than Q. The investment firm had offered Gessner the building as part of the neuroscientist’s recruitment package to the CIA, luring her in with the irresistible cachet of running her institute from such a unique and historic location.

  That’s not the real reason, Langdon surmised, sharing his growing suspicion that Finch had secured the bastion not as enticement for Gessner…but rather as something far more valuable.

  Another access for Threshold.

  Most medieval bastions included a unique architectural feature known as a poterne. From the Latin “posterior”—a poterne was a literal “back door”—a secret passageway used for emergency escapes.

  The ancient Estonian bastion in Tallinn, he told them, had a poterne carved four stories underground that stretched more than a mile away to the basement of a nearby monastery. The Slovenian mountaintop castle Predjama was rumored to have a six-story vertical shaft with a rudimentary pulley system “elevator” for restocking supplies, livestock, and troops.

  Crucifix Bastion, Langdon thought, was likely to have a poterne too. And considering the recent construction in Folimanka Park and the vast scope of the Threshold project, it made logical sense that a vertical shaft might exist beneath the bastion.

  Earlier, in the SUV, Langdon had quickly shown Katherine and Nagel on a map that a modern-day poterne—whether it existed previously or was drilled recently by construction crews—would descend directly to the edges of Folimanka Park and could potentially extend to the walls of the existing bomb shelter.

  The location of the bastion could not have been more perfect. Remote and discreet, Gessner’s lab offered a flawless cover story—plausible deniability for any personnel who came and went: they were simply working at the Gessner Institute.

  Let’s hope I’m right, Langdon now thought as he guided Katherine toward the bastion’s shattered entrance.

  This is a science lab?

  Katherine Solomon could scarcely believe her eyes as she followed Langdon down the luxurious, pink marble hallway into a lavish atrium with sumptuous couches, striking art, and floor-to-ceiling windows looking out at the skyline of Prague.

  Maybe I should work for the CIA, she thought, estimating that Gessner’s “waiting room” could have housed the entire IONS staff.

  Even so, Katherine felt a foreboding air about this space. If Langdon’s suspicions were correct, then this opulent “Gessner Institute” was actually camouflaging a darker purpose—a secret entrance to Threshold.

  Langdon strode to the far end of the space and went immediately to a ponderous wall sculpture made of welded metal blocks, stopping only inches away from it.

  What in the world is he doing?

  To Katherine’s surprise, Langdon grabbed the sculpture, heaved it to one side, and the sculpture slid silently along the wall to reveal a large alcove behind it. In the dim light beyond, she could see an elevator door.

  Why am I not surprised? she mused, hurrying across the room toward Langdon, who was holding the sliding artwork aside for her. As she arrived beside him, however, she noticed Langdon was staring at something behind her.

  “What is it?” she asked, glancing back over her shoulder.

  “That couch on the far wall…it’s cockeyed.”

  Katherine eyed the couch. Seriously, Robert? One edge of the long white couch was pulled at a slight angle away from the wall.

  “It was straight this morning when I sat on it,” he said, still staring at the couch. “I don’t know if I missed that, or if it was moved, or—”

  “Or if you forgot your OCD meds?”