"Then how do you read Qaran?" she finally asked. "It can only be read properly in Arabic."

How could I have known that the Koran is supposed to be read in Arabic? How could I have known that a language I did not speak would be the one triviality that could blow my cover? Of course, I could not have known, but with every answer to this friendly, curious tour guide's questions, I began to feel more and more as if I were digging my own tomb.

"My husband and I haven't been married very long," I said. "I only recently converted to Islam. I still need to learn Arabic in order to properly learn the Koran." I hoped it was an acceptable answer, but I was now feeling as if I were under a microscope. Should I have already learned Arabic in order to convert to Islam? I began sweating, even in the air-conditioned van.

"And your families accepted your marriage?" she asked.

"Yes. I agreed to convert to Islam."

"What were you before?"

"I was raised Catholic, but mostly I was an atheist. I didn't have any religion."

The woman shook her head. "Everyone should have religion. In my country, religion is from your family. It is who you are."

"Yes," I said, hoping to dig my way out. "I look forward to learning my husband's religion."

Then she asked the question I had no answer for. "But why you take Luxor tour without him?"

Of course, at that moment the benefit of hindsight came to me. It was far too late. I realized at that moment that I had seen many, many veiled women in Egypt since my arrival and that not one of them seemed to be out sightseeing alone. I had seen them with husbands and families at the various tourist attractions I had visited. I had seen them with husbands and families in the restaurant that morning. I had seen them with groups of other women. But I had not seen a single woman who was out alone for a seemingly frivolous purpose.

God, please, let us arrive at the next stop, I thought. Through the veil, I looked eagerly out the van's window, wondering how far away we still were from wherever we were going next.

I wasn't sure whether my friendly tour guide was still waiting for my answer, or if she had given up and was now mulling over our conversation. Perhaps she had already concluded that the woman before her was lying through her teeth. Perhaps she thought I was hiding from an abusive husband. Perhaps she thought I was hiding from something else.

Or perhaps she thought I was the missing American woman on the news. Perhaps she thought she should say something to someone.

The British man in our small tour group broke the uncomfortable silence. "I read a story a few years back about Cleopatra."

"Do tell!" his wife practically shouted, evidently dying for a change of subject.

"Do you know the legend about Cleopatra and the pearl?" he asked, speaking to his wife but also glancing around the van.

"Of course!" his wife said. "She bet Mark Antony that she could spend some exorbitant amount of money on one dinner. To do so, she dropped a pearl into her drink and then drank it! I always thought that was a myth."

"Everyone thought it was a myth," the man said. "Well, the ancients took it for fact, but in our time we all assumed it was impossible. A few years ago, I read this article. Someone proved it! A researcher at a university actually did the experiment and proved that Cleopatra could have dissolved a pearl in vinegar under the appropriate conditions."

"No!" The wife said in disbelief. "How?"

"According to the researcher, it doesn't take anything but vinegar and a pearl. Cleopatra might have softened the pearl first using some other technique we still haven't figured out yet."

The man laughed and threw an arm around his wife but then looked at my veiled face. He addressed me directly for the first time. "I bet you didn't know Queen Cleopatra was a chemist."

Cleopatra was busied in making a collection of all varieties of poisonous drugs, and, in order to see which of them were the least painful in the operation, she had them tried upon prisoners condemned to die.

Some relate that an asp was brought in amongst those figs... Others say that it was kept in a vase... But what really took place is known to no one. Since it was also said that she carried poison in a hollow bodkin, about which she wound her hair; yet there was not so much as a spot found... nor was the asp seen within the monument.

-Lives of the Noble Grecians and Romans Plutarch (ca. 46120 CE)

Chapter Twenty-Two.

It is amazing how even the most discerning eye can miss something obvious. And it is humbling when that discerning eye is one's own.

I had heard the story of Cleopatra and the pearl many times. And I remembered reading the Discovery News article back in 2010 when her pearl cocktail was scientifically proven possible.

There was another age-old legend having to do with the manner of Cleopatra's death. The legend held that she had committed suicide by enticing a snake-an Egyptian asp-to bite her. But this interpretation has been deemed impossible. It was not only Cleopatra who died a mysterious death that day but two of her female servants as well. Even if the snake could have been enticed to bite all three of them, no asp carries enough venom to kill three full-grown women.

The more accepted interpretation of their deaths is that Cleopatra self-administered some form of poison, also dosing her handmaidens with the same toxic formula. I even vaguely recalled having heard that she had studied various poisons beforehand to select those most effective and least painful.

I thought Alyssa was crazy, I remembered, reflecting upon our conversation in the Naples Archeological Museum. I thought her hypothesis that Cleopatra had been some sort of physician or research scientist was outrageous. I realized now that Alyssa's notion was not only plausible but, in fact, the most realistic interpretation of everything we have always known about Cleopatra.

As my tour van rolled across the Nile to the East Bank of Luxor, I thought about Raimondo di Sangro, the first man to attempt chemically unwinding the scrolls recovered from the Villa dei Papiri.

Like Cleopatra, di Sangro developed and utilized scientific methods, including specific solvents, that have baffled scientists for centuries. She dissolved a pearl to win a wager. He dissolved the marble of his own tomb to etch his epitaph. Cleopatra's chemical mystery was only solved in 2010. Di Sangro's has yet to be solved.

Di Sangro took his technologies to the grave.

Did Cleopatra do the same? I wondered. Could she have destroyed her own records before her death? The existence of the nardo document was proof that she had not. Perhaps she only wanted her enemies to believe that she did.

But di Sangro left behind proof of the existence of his methods: the chemically etched tombstone, the "anatomical machines"-human corpses mysteriously embalmed using beeswax and God knows what else.

He left behind a code for the enlightened to follow. My mind's eye saw again the statues in his chapel, the self-written legacy of Raimondo di Sangro. The Veiled Christ, a symbol of eternal life. Disillusion, the figure emerging from a binding net, a symbol of enlightenment. Light from darkness-a symbol of knowledge-like a grand lighthouse illuminating an even grander library. The veiled statue entitled Modesty-a symbol of wisdom. It was a clever representation of a veiled Isis, strategically placed in the exact location formerly occupied by a statue of the goddess herself in a Temple of Isis.

"Nature loves to hide," Modesty's veiled figure had been saying.

And that is why Alyssa became a follower of di Sangro, I recalled. Alyssa believed she had traced the nardo document from Cleopatra to him. And she was now trying to trace it forward in time to the present. To herself. To the veiled threats she had been receiving since its discovery. And to the code Cleopatra may also have left in plain sight for the enlightened-the code that would lead to the isotope.

How far has she gotten? I wondered.

She had been trying to tell me. When we were interrupted by the earthquake, she had gotten as far as the elder sister of Marie Antoinette, the woman in possession of the papyrus scrolls when Naples was invaded by Napoleon Bonaparte.

I needed to know the rest.

I glanced again at my Cairo watch. It was 1:00 p.m. Alyssa and Dante would not arrive in Luxor for several more hours.

What did Isis teach you? I asked Cleopatra, not realizing I was about to embark upon the first lesson.

The first ancient plant life I found was at Karnak Temple.

A relief on the wall at the Karnak Temple Complex depicted a large, diverse botanical garden. The relief dated to the Syrian campaigns of the pharaoh who had built that section of the temple fourteen hundred years before Cleopatra ruled Egypt.

I purchased several disposable cameras from a tout at the temple entrance and began taking photos of as many specimens as I could find. Some of the species looked like ordinary lilies, some like shrubs, and some like palms. Others looked as if they could have been grown in outer space. I had no idea how accurate they were. But it hardly mattered, as I had no idea what a nardo actually looked like.

I was in Luxor Museum when I saw the next plant the ancient Egyptians had deemed important enough to immortalize. I would have completely missed it. The plant was disguised.

This image had also originated in Karnak Temple. The scene was of a person making an offering to the sun. The sun's rays pointed down in straight lines at all angles from the large yellow globe, like those in a child's drawing. But the tips of the rays were hooked, and it was sheer luck that I was standing next to an English-speaking tour guide as he explained why to his group.

"The sunbeams are depicted as a papyrus plant," he was saying. "Papyrus was sacred to the ancient Egyptians and became the symbol of the Old Kingdom and the area we now know as Lower Egypt. Not only was the material used to make paper, a process dating back as far as 4000 BCE, it was also used to make rope, boats, and many other things the Egyptians relied upon to live."

Papyrus. I found myself tilting my head in an effort to visualize the sunbeams upright, as the plant would have grown. Then I shrugged. Aside from the interesting fact that the Egyptians have been making paper for six thousand years, I could find no real relevance to my quest in the image of the plant.

Is it significant that the papyrus is represented as the sun? I wondered, thinking again for a moment about the metaphor of light from darkness. It was certainly possible. Every piece of knowledge passed down in writing for thousands of years was owed to it.

"Did the Egyptians have an understanding of the distinctive properties of various plants, like the papyrus?" I asked the museum tour guide. "Or did they just take advantage of plants that were abundant?"

"They had a strong understanding," he said. "And they decided which ones were abundant. The Egyptian leaders strictly controlled what crops were grown throughout their kingdoms."

So the most important ones, I thought, were probably the most abundant.

As we exited the museum, my Luxor tour came to an end. I bid an awkward farewell to the nice British couple and to my tour guide. And I hoped that they would keep their mouths shut.

Again, I checked Jeff's e-mail. And again, there was no response from John. It was now early morning in San Diego.

John abruptly fell out of touch just as our San Diego laboratories were burglarized and Jeff and I were both declared missing, I realized. Was he the one who reported us missing?

Or was he the one who broke into the lab?

I wondered what Jeff had hidden within the files of our HER2 project. And I wondered if our physician friend could benefit from it.

Of course, there was also another possibility. There was the possibility that John had found the item that Jeff had been killed for and that he, too, was now dead.

I watched through my niqab from a distance as Dante Giordano stepped out of a taxi in the small Luxor square. He was alone. He sat down at an outdoor table of the cafe I had described to him over the phone.

I waited for fifteen minutes.

Dante appeared to grow increasingly agitated. He looked around the square. He looked at his watch. He leaned over and asked a passerby a question. The man shrugged and replied and then walked away.

Finally, I walked over to the cafe. I sat at a nearby table, but I faced the opposite direction. I unfolded an Arabic newspaper and pretended to read it.

Right to left, back to front, I had to remind myself.

When Dante extracted his cell phone, I could overhear his conversation. It was animated and sounded emotionally charged. But it was also in Italian. I could not understand a word.

Eventually, he stood up, took a last look around, and left the cafe. When I was reasonably confident he would not notice, I left the cafe as well and followed at a comfortable distance.

Dante looked lost. I was not surprised. He had come to Egypt on a moment's notice for the sole purpose of meeting with me, and I had not shown up. I assumed he was now wondering what to do with himself. I was curious to see what Dante Giordano would do with himself when he did not know anyone was watching.

He walked the streets for quite some time, scanning the hordes of tourists out and about in Luxor. He paused to step into a small souvenir shop, and when he stepped back out he was examining a large fold-out map. He found the waterfront and walked along the Nile, still scanning the crowd.

You won't find me, I thought.

He entered another shop, and this time a man followed him out. The man gestured toward a street corner, rambling in Arabic. Dante smiled and nodded, thanking the other man in Italian. Then he approached the corner and sat down.

He was sitting at a bus stop. And I knew it was time to move in.

When I knelt down to peer into his face, Dante looked up in shock. Instinctively, I leaned in toward him to whisper, but the effect was the opposite of what I had intended. He gasped audibly and lunged backward as if a large spider had just dropped from the sky to dangle before his eyes.

"Don't react," I said as quietly as I could, and his eyes widened again. Then he seemed to relax. He peered inward as if trying to see the eyes behind my veil. I could feel other eyes upon me as well.

"Katrina?" Dante said softly.

"Let's go," I said and stood up to leave, gathering the folds of my galabia and straining to see through the mud-caked porthole of my niqab.

"Where's Alyssa?" I asked as we walked.

"Katrina..." he said. "She..."

Just like that, I knew.

"She's dead, isn't she?"

"I went to the museum like you said," Dante said quietly. Tears had welled up in his eyes. "I couldn't find her, so I asked around. I found someone who worked with her. They said she had been shot and killed in her apartment."

My chest was constricting and I was struggling to breathe. I sat down on a swath of grass running along the bank of the Nile.

I saw Jeff lying dead and naked on the deck of my yacht. I saw a bloody, smeared handprint on a metal banister and a pistol silencer lying next to his body. Now Alyssa, too, had been killed in her own home. And for what? For a two-thousand-year-old message on papyrus? A message that-according to Alyssa-nobody even knew existed except for him, her, and me?

"Oh, God," I groaned, wondering if I had been her undoing, if I had guided her murderer toward her, if I had offered her up as a sacrifice just as I was now offering myself. And with Alyssa dead, my odds of finding the answers I needed had just become exponentially smaller.

I looked back at Dante but then had to look away.

"Katrina?"

I slowly came back to attention, with no idea how long I had been sitting there lost in thought.

"Yeah?"

"Why are you dressed like that?"

I took a breath. I had to tell him something. But I did not have to tell him everything.

"Because I think someone is after me," I said. "And because the best case scenario is that it's Middle Eastern law enforcement."

I paused and then continued, "That's why I wasn't able to meet you at the cafe earlier. I thought I was being followed. I was planning to call your cell again, but then I ran into you at that bus stop. Were you planning on leaving Egypt?"

Dante shrugged. "Uh, yeah, I guess so. I didn't know what else to do. I thought you stood me up." He smiled with a sincerity that made me question, just for a moment, if he could really be a killer.

A moment later, I bolted upright.

"Oh, fuck!" I said inelegantly.