She rushed out of the bedroom and across to the front door. Reaching for the dead bolt, she paused. She leaned forward instead and peeked through the door's peephole. It offered a fish-eye view of the hallway. A lone woman, black hair cut into a bob, stood outside the door. She wore a white jacket with the pharmacy logo on the lapel and carried a white paper bag, stapled with a clutch of receipt.

The woman reached out of view. The bell chimed again. The woman checked her watch and began to step away.

Harriet called through the door. "Hold for a moment!"

"Swan Pharmacy," the woman called back.

To be extra cautious, Harriet crossed to the telephone on an entryway table. She caught a look at herself in the wall mirror above it. She looked haggard, a melted wax candle of a woman. She tapped the button on the phone and rang the front desk in the lobby.

It was answered immediately.

"Phoenix Park. Front desk."

"This is room 334. I wanted to confirm a pharmacy delivery."

"Yes, ma'am. I checked her credentials three minutes ago. Is there a problem?"

"No. Not at all. I just wanted—"

A crash sounded from the bedroom behind her, followed by a spat of cursing. Jack had finally opened the bathroom door.

The receptionist spoke in her ear. "Is there anything else I can do for you, ma'am."

"No. Thank you." She hung up the phone.

"Harriet!" her husband called, a note of distress behind the anger.

"I'm here, Jack."

The doorbell chimed again.

Frazzled, Harriet undid the door's dead bolt, hoping Jack would not fuss about taking his pills. She pulled open the door.

The delivery woman lifted her face, smiling—but there was no warmth, only a feral amusement. A shock of recognition froze Harriet. It was the woman who had attacked them at the safe house. Before Harriet could move, the woman kicked the door the rest of the way open.

Startled, the edge struck Harriet in the shoulder and knocked her into a stumbling fall onto the hard tile. She tried to absorb the impact with an outstretched arm—but her wrist exploded under her with a sharp snap. Fiery pain shot up her arm.

Gasping out, half on her hip, she rolled away.

Jack stalked out of the bedroom, only in his boxers.

"Harriet... ?"

Still addled, Jack took too long to register the situation.

The woman stepped over the threshold and raised a thick-barreled pistol. She pointed the weapon at Jack. "Here's your medication."

"No," Harriet moaned.

The woman pulled the trigger. A snapping pop of electricity exploded from the barrel. Something spat past Harriet's ear, trailing wire. It struck Jack in the bare chest, sparking and crackling blue in the dim light.

Taser.

He gagged, arms flying out—and crashed backward.

He didn't move.

In the stunned silence a Fox News announcer whispered from the half-muted television: "Metro police are still continuing a manhunt for Grayson Pierce, wanted in connection to the arson and bombing of a local D.C. home."

8:32 A.M. Istanbul

Alone at the roof rail Gray struggled to think of some secure channel to communicate to Washington. About the dangers at Christmas Island. He would have to be circumspect, some private communication that would not spread beyond Painter. But how? Who was to say that the Guild was not monitoring all manner of communication?

Seichan spoke behind him, back at the table. Her words were not directed at Gray. "Monsignor, you still have not explained why you called us to Istanbul. You claimed to have understood the angelic inscription."

Curiosity drew Gray back to the table, but he could not sit. He stood between Seichan and Vigor.

The monsignor swung up his backpack and settled it in his lap. He fished through it and pulled out a notebook, flipping it open on the table. Across the page was a charcoal-etched line of angelic letters.

"Here is the inscription on the floor of the Tower of Wind," Vigor said. "Each letter of this alphabet corresponds to a specific tonal word. And according to the father of angelic script, Trithemius, when combined in the right sequence, such groupings could open a direct line to a specific angel."

"Like long-distance dialing," Kowalski muttered from the other side of the table.

With a nod, Vigor flipped the sheet to the next page. "I went ahead and marked the name for each letter."

Gray shook his head, not seeing any pattern.

Vigor slipped out a pen and drew a line under the first letter of each name, reciting as he did so. "A. I. G. A. H."

"Is that some angel's name?" Kowalski asked.

"No, not an angel, but it is a name," Vigor said. "What you have to understand is that Trithemius based his alphabet on Hebrew, claiming power in the Jewish letters. Even today, practitioners of Kabbalah believe that there is some form of divine wisdom buried in the shapes and curves of the Hebrew alphabet. Trithemius just claimed his angelic script was the purest distillation of Hebrew."

Gray leaned closer, beginning to understand the direction of Vigor's track. "And Hebrew is read opposite from English. From right to left."

Seichan traced a finger across the paper and read backward. "H. A. G. I. A."

"Hagia," Vigor pronounced carefully. "The word means 'divine' in Greek."

Gray's eyes had narrowed—then widened with sudden understanding.

Of course.

"What?" Siechan asked.

Kowalski scratched the stubble on his head, equally clueless.

Vigor stood and drew them all up. He walked them to face the city. "On his journey home, Marco Polo crossed through Istanbul, named Constantinople at the time. Here is where he crossed from Asia and finally reentered Europe, a significant crossroads of sorts."

The monsignor pointed out to the city, toward one of the ancient monuments. Gray had noted it before. A massive flat-domed church, half covered in black scaffolding as restoration work was under way.

"Hagia Sophia," Gray said, naming the structure.

Vigor nodded. "It was once the largest Christian church in all the world. Marco himself commented on the wonders of its airy spaces. Some people mistake Hagia Sophia to mean 'Saint Sophia,' but in fact, the true name of the structure is the Church of Divine Wisdom, which can also be interpreted as the Church of Angelic Wisdom."

"Then that's where we must go!" Seichan said. "The first key must be hidden there." She swung away.

"Not so fast, young lady," Vigor scolded.

The monsignor returned to his backpack, reached inside, and drew out a cloth-wrapped object. Gently resting it on the table, he peeled back the layers to reveal a flat bar of dull gold. It appeared very old. It bore a hole at one end, and its surface was covered in a cursive script.

"Not angelic," Vigor said, noting Gray's attention to the lettering. "It's Mongolian. It reads, 'By the strength of the eternal heaven, holy be the Khan's name. Let he who pays him not reverence be killed.'"

"I don't understand," Gray said, crinkling his brow. "Did this belong to Marco Polo? What is it?"

"In Chinese, it is called apaitzu. In Mongolian, a gerege."

Three blank faces stared back at Vigor.

Vigor nodded to the object. "In the modern vernacular, it's a VIP passport. A traveler bearing this superpassport could demand horses, supplies, men, boats, anything from the lands governed by Kublia Khan. To refuse such aid was punishable by death. The Khan granted such passes to those ambassadors who traveled in his service."

"Nice," Kowalski whistled—but from the glint in the man's eyes, Gray suspected it was the gold more than the story that had won the man's awe.

"And the Polos were given one of these passports?" Seichan asked.

"Three of them, in fact. One for each Polo. Marco, his father, and his uncle. In fact, there is an anecdote concerning these passports. A famous one. When the Polos arrived back in Venice, it was said no one recognized them. The trio came worn, tired, in a single ship. Looking little better than beggars. None would believe them to be the long-vanished Polos. Upon stepping to shore, the trio sliced open the seams of their clothes, and a vast wealth of emeralds, rubies, sapphires, and silver spilled out. Included in this treasure trove were the three golden paitzus, described in great detail. But after this story, the golden passports vanished away. All three of them."

"The same number as the map's keys," Gray commented.

"Where did you find this?" Seichan asked. "In one of the Vatican museums?"

"No." Vigor tapped the open notebook with the angelic script. "With the help of a friend, I discovered it under the marble tile upon which this inscription was written. In a secret hollow beneath the marble."

Like the friar's cross, Gray realized. Buried in stone.

Seichan swore slightly. Again the prize had been right under her nose all along.

Vigor continued, "I believe this is one of the very paitzus granted to the Polos." He faced them all. "And I believe this is the first key."

"So the clue leading to Hagia Sophia . . ." Gray began.

"It's pointing to the second key," Vigor finished. "Two more missing passports, two more missing keys."

"But how can you be so sure?" Seichan asked.

Vigor flipped the gold bar over. Inscribed in great detail, a single letter adorned the back side. An angelic letter.

Vigor tapped the letter. "Here is the first key."

Gray knew he was right. He glanced up, toward the massive church. Hagia Sophia. The second key had to be hidden there, but it was a huge structure. It would be like finding a golden needle in a haystack. It could take days.

Vigor must have read his worry. "I already have someone scouting ahead at the church. An art historian from the Vatican who helped me back at the Tower of Wind with the angelic riddle."

Gray nodded. As he studied the single letter, he could not shake a deeper worry. For his two friends. Monk and Lisa. Already in harm's way. If he could not contact Washington safely, perhaps there was another way he could help his friends: by beating the Guild to whatever lay at the end of this mystery.