“Which you believe.”

  “I do. We can’t yet prove this cosmic realm exists, but it seems to be regularly glimpsed by minds in altered states. Unfortunately, these experiences are fleeting, uncontrolled, subjective, and often nonrepeatable—making them suspect scientifically.”

  “And easy targets for skeptics.”

  “Yes. We have no quantifiable method, machine, or technology capable of receiving signals from the cosmic realm. Only the brain can do that.” She gave a casual shrug. “And so I proposed a hypothetical chip that could piggyback on a brain, lower its GABA levels, widen its bandwidth, and turn it into a far more powerful receiver.”

  Langdon stared at her in awe. Not only was Katherine’s idea indisputably brilliant, it might finally explain exactly why the CIA was panicked about her manuscript.

  What if Katherine was about to publish a book that described an ultrasecret chip the CIA is already building?!

  “Katherine,” he said, “Threshold is taking consciousness study to the next dimension, and your book might have been about to blow the lid off the centerpiece of their secret technology.”

  “There’s no chance of that,” she said. “Like I said, the chip I described is not buildable. It’s interesting conceptually, but strictly hypothetical. The technical barriers to its construction are immovable—specifically this: regulating system-wide levels of a neurotransmitter would require complete physical integration with the brain’s neural network…and the brain has over a hundred trillion synapses to monitor.”

  “But scientific progress is accel—”

  “Robert, believe me, complete physical integration is unachievable. It would be the equivalent of directly wiring every single lightbulb on earth to one switch, a million times over. It’s genuinely impossible.”

  “So was splitting the atom…” Langdon retorted. “But science has a way of figuring things out, especially with unlimited budgets. Remember the Manhattan Project?”

  “Huge difference…Nuclear technology already existed in 1940. Uranium existed. Scientists just pulled it all together. The chip I proposed requires technology and materials that don’t even exist on earth. Before we can even talk about integrating with the brain’s dendritic tree, someone has to invent a nanoelectric biofilament.”

  “A nanoelectric what?”

  “Exactly—it’s not even a real thing. I invented it in my book as a way to talk about a technology that does not exist. It would be a futuristic, ultrathin, flexible filament made of biocompatible material that can carry both electronic and ionic signals. Essentially, an artificial neuron.”

  “And artificial neurons are not possible to create?”

  “No, we’re not even close. Last year, two guys in Sweden made international headlines by persuading a Venus flytrap to open and close by chemically stimulating a neuron. Just a single binary impulse—and yet it sent scientific shock waves around the world. That’s the state of the art, Robert, and it’s generations away from an artificial neuron.”

  Langdon was already moving across the room toward the window of the biology lab he had seen several minutes earlier. “Theoretically speaking,” he said, “would you build artificial neurons…or grow them?”

  She thought a moment. “A nanoelectric biofilament? Well, it would be a biological filament, so you’d have to grow them.”

  Langdon stopped at the window and peered at the machine with hundreds of long glass vials and tubes. “In a liquid suspension, I imagine?”

  “Yes. Fragile microstructures are always cultivated in suspension.”

  “Then I think you should come over here,” he said, waving her to the window. “It looks like Threshold is growing something…and I’m guessing it’s not arugula.”

  CHAPTER 103

  Everett Finch burst through the compromised entrance of Crucifix Bastion and stormed down the hall into the glass-walled atrium. Where the hell is everyone?! Enraged to find no trace of Housemore or the embassy’s promised security detail, he pulled out his personal RFID key card and headed for the elevator.

  As he crossed the room, the key card’s biometric sensors activated in his fingertips, but he stopped short, reminded that there was no possible way for Housemore—or anyone for that matter—to access the elevator down to Threshold.

  She must be upstairs…or else she left the bastion for some reason?

  He dialed Housemore’s line one last time.

  As soon as Finch placed the call, a phone began chirping nearby. Odd. The sound seemed to be emanating from a couch against the far wall. Did Housemore lose her phone? At least it would explain why she hadn’t answered earlier.

  Finch strode to the couch but saw no phone. The ringing had stopped, and he called again. Once more, a phone began to chirp. Is it beneath the couch?

  Finch crouched down to look under the stylish furniture.

  As he stared into the dark space, he knew instantly that Threshold was under attack.

  Staring back at him were two dead eyes—the lifeless gaze of his field officer Susan Housemore.

  In the frigid vault, The Golěm gazed at the powerful machine sitting before him. The device’s gleaming metal body was a bulbous ring of polished aluminum that occupied nearly the entire concrete chamber. Five meters across and one meter tall, the machine resembled a giant metal donut. The unusual donut shape—technically “toroidal,” according to The Golěm’s research this morning—was apparently the most efficient shape in which to wrap superconducting coils if one wanted to create a magnetic field capable of storing vast amounts of energy.

  SMES, he thought. Superconducting magnetic energy storage.

  This was the secret source of Threshold’s power.

  The Golěm had learned this morning that energy fed into the toroidal magnetic field would race in loops indefinitely with no degradation and could be siphoned off as needed. The only prerequisite was to keep the superconducting coils cold.

  Extremely cold.

  The critical temperature for its coils was somewhere below negative-260 Celsius, and if the coils rose even slightly above this temperature, they lost superconductivity and began resisting the current. That resistance caused rapid heating of the coils, which in turn caused more resistance, and within seconds the feedback loop blossomed out of control…resulting in a dangerous event known as a quench.

  To prevent quenching, the coils were continuously flushed in a bath of the coldest liquid on earth. Liquid helium.

  He gazed past the SMES to the adjoining chamber, where, locked within a Mu-metal mesh cage, stood twelve austenitic, stainless-steel tanks of liquid helium. Each of the five-hundred-gallon, Cryofab flasks stood as tall as The Golěm and was equipped with a cryogenic bayonet and vacuum-jacketed piping that transported the cold liquid into the SMES to keep the superconductors cold.

  Liquid helium, by most measurements, was harmless—nonexplosive, nonflammable, and nonpoisonous. Its sole dangerous quality was possessing the lowest boiling point of any substance known to man…a frigid negative-270 Celsius. This meant that if the helium was permitted to “warm up” above negative-270 Celsius—already near absolute zero—it immediately boiled and converted to helium gas.

  The gas itself was also harmless, but the danger lay in the physics of the conversion process. Liquid helium’s conversion to gas was shockingly fast and violent…and, as it turned out, it was the entire reason Threshold had co-opted the R2-D2 vent in Folimanka Park.

  When liquid helium converted to gas, its volume multiplied by a mind-boggling ratio of 1 to 750. This meant that the liquid helium in this vault, if released, would rapidly convert to enough gas to fill seven Olympic swimming pools.

  In an unvented space, the new volume would have nowhere to go, and the pressure buildup would happen so fast that it would create a “pressure bomb”—a near-instantaneous, violent outward force expanding in all directions. In a desperate attempt to make room for itself, the gas would blow apart whatever constrained it, resulting in a shock wave much like that of a tactical nuclear weapon, tearing through everything in a given radius.

  To mitigate risk, all facilities using liquid helium, including hospitals with MRI machines, were required to install a “quench vent”—a ventilation pipe that ascended up through the roof of the building—to ensure that, in the event of an inadvertent helium leak, the rapidly expanding gas would have a safe alternate route to escape…rather than blowing up the building. Threshold’s quench vent was massive, but then again, so was the quantity of liquid helium stored down here.

  The Golěm gazed again past the SMES to the twelve Cryofab flasks. More than twenty thousand liters of helium, he had calculated. The expansion potential was almost incalculable.

  Catastrophic explosions with liquid helium, he had learned online, were fairly common—including SpaceX’s Falcon 9 rocket, CERN’s Large Hadron Collider, and even a veterinary clinic in New Jersey whose MRI had a small leak and exploded.

  The Golěm knew that if this SMES quenched unexpectedly, the liquid helium loaded into the system would instantly boil off in a torrent of expanding gas racing up the conduit and shooting skyward over Prague in a geyser of freezing-cold helium.

  Most likely blasting off R2-D2’s head in the process.

  The liquid helium loaded into the SMES machine at any time represented a very small portion of the total volume contained in the tanks. The Golěm could not begin to imagine what would happen if all the helium in this facility were released at once…converting from liquid to gas in an instant.

  Such an event had never occurred. Ever. Anywhere.

  There were too many fail-safes.

  Helium flasks were extremely robust with multiple safety features. Built like giant Thermoses, their double-hulled “Dewar” design employed nature’s most efficient insulator—a pure vacuum—to ensure the liquid inside stayed cold enough never to convert to gas. For additional safety, each flask stored its liquid under extremely high pressure. This raised the helium’s boiling point, offering a wider margin of error before it hit critical temperature.

  The flask’s final safety measure was a “rupture disk”—a tiny copper disk built into the shell of the tank. An intentional weak spot, the disk was calibrated to rupture if the internal pressure climbed too high…thus averting a cataclysmic tank explosion.

  Although rupture disks were designed to explode outward, they would also rupture inward if the pressure outside a canister became too great. Of course, that never happened because nobody was ever careless enough to store liquid helium in an airtight space.

  Considering these three fail-safes, the probability of multiple tank failures at the same moment carried a statistical probability of zero.

  It simply could not happen.

  Not without help.

  Reflecting on the horrors inflicted on Sasha by Threshold, The Golěm took a final look at the quietly humming SMES device, savoring the irony. This machine was the secret source of Threshold’s power…and was about to become the agent of its destruction.

  CHAPTER 104

  Having entered the bio lab with Langdon, Katherine was carefully examining the sophisticated machine before her.

  Artificial neurons don’t exist. Not yet.

  This had always been Katherine’s belief…but now she was not so sure. While the machine did indeed look like an elaborate hydroponic incubator, she had no way to know, with her naked eye, what was in the vials of liquid.

  It’s impossible…isn’t it?

  Much of Katherine’s postgraduate work in brain science had centered on neurochemistry, studying the specific chemical mechanisms by which the brain’s neural network functioned. Artificial neurons, in concept, had first been proposed in 1943 by American scientists Warren McCulloch and Walter Pitts—but the realization of that concept had always seemed a distant dream. There was a common quip among biologists: Humans will inhabit Mars long before we build an artificial neuron.

  “Check those manuals?” she said, motioning to a bookcase across the room. “See if you see anything about this incubator or what they’re growing in here. I’ll check the drawers.”

  As Langdon headed to the bookcase, Katherine began rifling through a set of file drawers built into the room’s glistening worktable. Most meticulous laboratories, including the Institute of Noetic Sciences, created a “protocol book” for every project—a hard copy set of procedural guidelines to ensure consistency and reproducibility of results. This is what Katherine hoped to find, but she found nothing of much interest within the drawers.

  It was not until she discovered a recessed “flat tray” drawer in the table that she found anything promising…including a heavy black three-ring binder. Although it was far too thick to be the protocol book she was looking for, she felt a chill when she saw the words emblazoned on the cover.

  TOP SECRET

  Property of Central Intelligence Agency

  Katherine immediately hoisted the binder onto the table and opened it.

  Please tell us something…

  As she skimmed the first few pages, she was startled to learn that the authors of this binder came from the prestigious Laboratory of Organic Electronics (LOE) in Sweden. The CIA recruited from LOE?! In the quest to produce artificial neurons, LOE was one of the world’s leading think tanks. Katherine had mentioned their Venus flytrap breakthrough only minutes ago!

  Spellbound, she flipped through the various sections of the binder, reading the headers. She saw a number of familiar topics, but then her eye hit on one that stopped her cold.

  MODULATION VIA MIXED ION-ELECTRON CONDUCTING POLYMERS

  Modulation? She immediately began scanning the section. Did they really solve modulation?!

  One of the most daunting hurdles in the quest to build an artificial neuron was to mimic “ion modulation”—a neuron’s unique ability to activate and deactivate sodium ion channels. And yet if this header was to be believed, ion modulation was now possible.

  But…how?!

  Heart racing, Katherine began reading about Threshold’s solution to the modulation problem. Everything about it made perfect sense to her…almost too perfect…and the further she read, the harder it became for her to breathe.

  No…no…this can’t be!

  “Katherine?” Langdon repeated, having joined her at the table after hearing her gasp a few moments ago. “Are you okay?”

  But she made no reply, her eyes riveted to the binder as she flipped pages, one after another, muttering quietly to herself.

  Langdon peered over her shoulder, trying to see what was upsetting her, but the page header meant nothing to him. Modulation via mixed ion-electron conducting polymers?

  As the seconds wore on, Langdon sensed Katherine was in a state of mild shock, and he finally placed a hand on her arm. “What is it?”

  She spun abruptly toward him, her eyes full of fire. “What is it? Threshold is using synthesized BBL as an organic electrochemical transistor! They cast it into a thin film and dissolved it in methanesulfonic—”

  “Slow down—what?”

  “BBL! They’re using it in the artificial neurons! That was my idea, Robert!”

  “First of all, what is BBL?”

  “Benzimidazobenzophenanthroline. It’s a highly conductive polymer that is uniquely tough and also elastic.”

  “Okay, and…?”

  “And they are implementing polycondensation to synthesize BBL—which was my suggestion. The result is a substance that is vastly conductive to electrons…much like a neuron.” She flipped a page of the binder. “Look! The chemical protocols in this binder are exactly the protocols I describe in my manuscript! Down to the finest details! I suggested modifying conductance by adding three millimolars of glutamine to the electrolyte solution—and that’s exactly what they are doing!”

  Langdon wasn’t following much of this, but clearly Katherine believed she had identified a point of direct intersection between her manuscript and the Threshold project. That’s what we came here for.

  “Katherine,” he said quietly, “can you take a breath and explain to me, in simple English, what’s going on?”

  She nodded, exhaling. “Sorry, yes,” she said, lowering her voice. “Simply stated, my book theorized how this technology might actually be produced someday. I specifically proposed weaving the fabricated substance into a neural ‘mesh’ that could be pulled over the brain like a cap…a sheath of neurons in direct contact with the brain.” She sighed. “And…most incredibly, that is exactly what they are doing here. I just…well, I can’t believe it.”

  “So you wrote expressly about artificial neurons?”

  “I did. When I proposed a hypothetical brain chip to regulate GABA, I knew the chip could not be built without artificial neurons, so I included my best guess at how neurons might be fabricated someday…in the distant future.”

  That future is apparently now, Langdon realized, glancing down at the binder. “And you think Threshold actually built the GABA chip you proposed?”

  “No, no,” she said, shaking her head. “I have no idea what chip they built—but I’m pretty certain it would not be the one I proposed. If they have artificial neurons, the sky’s the limit; they could build literally whatever they dream up. Artificial neurons are the critical leap required for full H2M integration. You’ve got to understand, Robert…” She looked him straight in the eyes. “This neuron technology is the key to the future. It changes everything.”

  Langdon had no doubt she was correct; he had read more than once that futurists predicted an artificial neuron breakthrough would usher in an astonishing era of direct brain-to-brain communication, memory augmentation, accelerated learning, and even the ability to record our dreams at night and play them back in the morning.

  Most disturbing to Langdon, however, was the forecast hailed as “the ultimate social media”—humans making full-sensory recordings of their own experiences…and sharing their own personal “channels” directly with other minds. In essence, people would be able to relive the sights, sounds, smells, and feelings of someone else’s experience. Of course, it would not take long for black-market libraries to offer particularly shocking, titillating, or grisly memories. The 1990s cyberpunk movie Strange Days had ventured into this dark world…presciently, it now seemed.