He was starting to suspect that the purpose of this visit was not what it appeared to be. Why are they really here?

“One more flight,” Mirsat announced cheerily as they reached the landing. “Upstairs we shall find the tomb of Enrico Dandolo, and of course”—he paused, eyeing Langdon—“the famed Deesis Mosaic.”

Not even a flinch.

Langdon, it appeared, was not, in fact, here for the Deesis Mosaic at all. He and his guests seemed inexplicably fixated on Dandolo’s tomb.

CHAPTER 89

As Mirsat led the way up the stairs, Langdon could tell that Brüder and Sinskey were worried. Admittedly, ascending to the second floor seemed to make no sense. Langdon kept picturing Zobrist’s subterranean video … and the documentary film about the submerged areas beneath Hagia Sophia.

We need to go down!

Even so, if this was the location of Dandolo’s tomb, they had no choice but to follow Zobrist’s directions. Kneel within the gilded mouseion of holy wisdom, and place thine ear to the ground, listening for the sounds of trickling water.

When they finally reached the second level, Mirsat led them to the right along the balcony’s edge, which offered breathtaking views of the sanctuary below. Langdon faced front, remaining focused.

Mirsat was talking fervently about the Deesis Mosaic again, but Langdon tuned him out.

He could now see his target.

Dandolo’s tomb.

The tomb appeared exactly as Langdon remembered it—a rectangular piece of white marble, inlaid in the polished stone floor and cordoned off by stanchions and chains.

Langdon rushed over and examined the carved inscription.

HENRICUS DANDOLO

As the others arrived behind him, Langdon sprang into action, stepping over the protective chain and placing his feet directly in front of the tombstone.

Mirsat protested loudly, but Langdon continued, dropping quickly to his knees as if preparing to pray at the feet of the treacherous doge.

Next, in a move that elicited shouts of horror from Mirsat, Langdon placed his palms flat on the tomb and prostrated himself. As he lowered his face to the ground, Langdon realized that he looked like he was bowing to Mecca. The maneuver apparently stunned Mirsat, who fell mute, and a sudden hush seemed to pervade the entire building.

Taking a deep breath, Langdon turned his head to the right and gently pressed his left ear to the tomb. The stone felt cold on his flesh.

The sound he heard echoing up through the stone was as clear as day.

My God.

The finale of Dante’s Inferno seemed to be echoing up from below.

Slowly, Langdon turned his head, gazing up at Brüder and Sinskey.

“I hear it,” he whispered. “The sounds of trickling water.”

Brüder vaulted the chain and crouched down beside Langdon to listen. After a moment he was nodding intently.

Now that they could hear the water flowing downward, one question remained. Where is it flowing?

Langdon’s mind was suddenly flooded with images of a half-submerged cavern, bathed in an eerie red light … somewhere beneath them.

Follow deep into the sunken palace …

for here, in the darkness, the chthonic monster waits,

submerged in the bloodred waters …

of the lagoon that reflects no stars.

When Langdon stood and stepped back over the stanchions, Mirsat was glaring up at him with a look of alarm and betrayal on his face. Langdon stood almost a foot taller than the Turkish guide.

“Mirsat,” Langdon began. “I’m sorry. As you can see, this is a very unusual situation. I don’t have time to explain, but I have a very important question to ask you about this building.”

Mirsat managed a weak nod. “Okay.”

“Here at Dandolo’s tomb, we can hear a rivulet of water flowing somewhere under the stone. We need to know where this water flows.”

Mirsat shook his head. “I don’t understand. Water can be heard beneath the floors everywhere in Hagia Sophia.”

Everyone stiffened.

“Yes,” Mirsat told them, “especially when it rains. Hagia Sophia has approximately one hundred thousand square feet of rooftops that need to drain, and it often takes days. And usually it rains again before the drainage is complete. The sounds of trickling water are quite common here. Perhaps you are aware that Hagia Sofia sits on vast caverns of water. There was a documentary even, which—”

“Yes, yes,” Langdon said, “but do you know if the water that is audible here at Dandolo’s tomb flows somewhere specific?”

“Of course,” Mirsat said. “It flows to the same place that all the water shedding from Hagia Sophia flows. To the city cistern.”

“No,” Brüder declared, stepping back over the stanchion. “We’re not looking for a cistern. We’re looking for a large, underground space, perhaps with columns?”

“Yes,” Mirsat said. “The city’s ancient cistern is precisely that—a large underground space with columns. Quite impressive actually. It was built in the sixth century to house the city’s water supply. Nowadays it contains only about four feet of water, but—”

“Where is it!” Brüder demanded, his voice echoing across the empty hall.

“The … cistern?” Mirsat asked, looking frightened. “It’s a block away, just east of this building.” He pointed outside. “It’s called Yerebatan Sarayi.”

Sarayi? Langdon wondered. As in Topkapi Sarayi? Signage for the Topkapi Palace had been ubiquitous as they were driving in. “But … doesn’t sarayi mean ‘palace’?”

Mirsat nodded. “Yes. The name of our ancient cistern is Yerebatan Sarayi. It means—the sunken palace.”

CHAPTER 90

The rain was falling in sheets as Dr. Elizabeth Sinskey burst out of Hagia Sophia with Langdon, Brüder, and their bewildered guide, Mirsat.

Follow deep into the sunken palace, Sinskey thought.

The site of the city’s cistern—Yerebatan Sarayi—was apparently back toward the Blue Mosque and a bit to the north.

Mirsat led the way.

Sinskey had seen no other option but to tell Mirsat who they were and that they were racing to thwart a possible health crisis within the sunken palace.

“This way!” Mirsat called, leading them across the darkened park. The mountain of Hagia Sophia was behind them now, and the fairy-tale spires of the Blue Mosque glistened ahead.

Hurrying beside Sinskey, Agent Brüder was shouting into his phone, updating the SRS team and ordering them to rendezvous at the cistern’s entrance. “It sounds like Zobrist is targeting the city’s water supply,” Brüder said, breathless. “I’m going to need schematics of all conduits in and out of the cistern. We’ll run full isolation and containment protocols. We’ll need physical and chemical barriers along with vacuum—”

“Wait,” Mirsat called over to him. “You misunderstood me. The cistern is not the city water supply. Not anymore!”

Brüder lowered his phone, glaring at their guide. “What?”

“In ancient times, the cistern held the water supply,” Mirsat clarified. “But no longer. We modernized.”

Brüder came to a stop under a sheltering tree, and everyone halted with him.

“Mirsat,” Sinskey said, “you’re sure that nobody drinks the water out of the cistern?”

“Heavens no,” Mirsat said. “The water pretty much just sits there … eventually filtering down into the earth.”

Sinskey, Langdon, and Brüder all exchanged uncertain looks. Sinskey didn’t know whether to feel relieved or alarmed. If nobody comes in regular contact with the water, why would Zobrist choose to contaminate it?

“When we modernized our water supply decades ago,” Mirsat explained, “the cistern fell out of use and became just a big pond in an underground room.” He shrugged. “These days it’s nothing more than a tourist attraction.”

Sinskey spun toward Mirsat. A tourist attraction? “Hold on … people can go down there? Into the cistern?”

“Of course,” he said. “Many thousands visit every day. The cavern is quite striking. There are boardwalks over the water … and even a small café. There’s limited ventilation, so the air is quite stuffy and humid, but it’s still very popular.”

Sinskey’s eyes locked on Brüder, and she could tell that she and the trained SRS agent were picturing the same thing—a dark, humid cavern filled with stagnant water in which a pathogen was incubating. Completing the nightmare was the presence of boardwalks over which tourists moved all day long, just above the water’s surface.

“He created a bioaerosol,” Brüder declared.

Sinskey nodded, slumping.

“Meaning?” Langdon demanded.

“Meaning,” Brüder replied, “that it can go airborne.”

Langdon fell silent, and Sinskey could see that he was now grasping the potential magnitude of this crisis.

An airborne pathogen had been on Sinskey’s mind as a possible scenario for some time, and yet when she believed that the cistern was the city’s water supply, she had hoped maybe this meant that Zobrist had chosen a water-bound bioform. Water-dwelling bacteria were robust and weather-resistant, but they were also slow to propagate.

Airborne pathogens spread fast.

Very fast.

“If it’s airborne,” Brüder said, “it’s probably viral.”

A virus, Sinskey agreed. The fastest-spreading pathogen Zobrist could choose.

Releasing an airborne virus underwater was admittedly unusual, and yet there were many life-forms that incubated in liquid and then hatched into the air—mosquitoes, mold spores, the bacterium that caused Legionnaires’ disease, mycotoxins, red tide, even human beings. Sinskey grimly pictured the virus permeating the cistern’s lagoon … and then the infected microdroplets rising into the damp air.

Mirsat was now staring across a traffic-jammed street with a look of apprehension on his face. Sinskey followed his gaze to a squat, red-and-white brick building whose single door was open, revealing what looked to be a stairwell. A scattering of well-dressed people seemed to be waiting outside under umbrellas while a doorman controlled the flow of guests who were descending the stairs.

Some kind of underground dance club?

Sinskey saw the gold lettering on the building and felt a sudden tightness in her chest. Unless this club was called the Cistern and had been built in A.D. 523, she realized why Mirsat was looking so concerned.

“The sunken palace,” Mirsat stammered. “It seems … there is a concert tonight.”

Sinskey was incredulous. “A concert in a cistern?!”

“It’s a large indoor space,” he replied. “It is often used as a cultural center.”

Brüder had apparently heard enough. He dashed toward the building, sidestepping his way through snarled traffic on Alemdar Avenue. Sinskey and the others broke into a run as well, close on the agent’s heels.

When they arrived at the cistern entrance, the doorway was blocked by a handful of concertgoers who were waiting to be let in—a trio of women in burkas, a pair of tourists holding hands, a man in a tuxedo. They were all clustered together in the doorway, trying to keep out of the rain.

Sinskey could hear the melodic strains of a classical music composition lilting up from below. Berlioz, she guessed from the idiosyncratic orchestration, but whatever it was, it felt out of place here in the streets of Istanbul.

As they drew closer to the doorway, she felt a warm wind rushing up the stairs, billowing from deep inside the earth and escaping from the enclosed cavern. The wind brought to the surface not only the sound of violins, but the unmistakable scents of humidity and masses of people.

It also brought to Sinskey a deep sense of foreboding.

As a group of tourists emerged from the stairs, chatting happily as they exited the building, the doorman allowed the next group to descend.

Brüder immediately moved to enter, but the doorman stopped him with a pleasant wave. “One moment, sir. The cistern is at capacity. It should be less than a minute until another visitor exits. Thank you.”

Brüder looked ready to force his way in, but Sinskey placed a hand on his shoulder and pulled him off to one side.

“Wait,” she commanded. “Your team is on the way and you can’t search this place alone.” She motioned to the plaque on the wall beside the door. “The cistern is enormous.”

The informational plaque described a cathedral-size subterranean room—nearly two football fields in length—with a ceiling spanning more than a hundred thousand square feet and supported by a forest of 336 marble columns.

“Look at this,” Langdon said, standing a few yards away. “You’re not going to believe it.”

Sinskey turned. Langdon motioned to a concert poster on the wall.

Oh, dear God.

The WHO director had been correct in identifying the style of the music as Romantic, but the piece that was being performed had not been composed by Berlioz. It was by a different Romantic composer—Franz Liszt.

Tonight, deep within the earth, the Istanbul State Symphony Orchestra was performing one of Franz Liszt’s most famous works—the Dante Symphony—an entire composition inspired by Dante’s descent into and return from hell.

“It’s being performed here for a week,” Langdon said, scrutinizing the poster’s fine print. “A free concert. Underwritten by an anonymous donor.”

Sinskey suspected that she could guess the identity of the anonymous donor. Bertrand Zobrist’s flair for the dramatic, it seemed, was also a ruthless practical strategy. This week of free concerts would lure thousands more tourists than usual down into the cistern and place them in a congested area … where they would breathe the contaminated air, then travel back to their homes both here and abroad.

“Sir?” the doorman called to Brüder. “We have room for a couple more.”