I watched them walking a moment longer. Then I turned and walked away without looking back.

"There's been a change of plan," I said. "We can't wait until tonight."

"Let me check my schedule." Aldo de Luca looked dramatically around the homeless shelter before returning his gaze to me. "What do you need me to do?"

His eyes were as cold as ever.

An hour later, I returned to the underground lab accompanied by a handsome professional in a shirt and tie. A handful of devoted scientists remained at their work, apparently uninterrupted by the earthquake-an event that now seemed to me like days rather than hours earlier.

"Is Dr. Iacovani still here?" I asked the first person I saw.

"No," the boy said. "She left a while ago." His English was perfect, but his accent was German. "I think she went back to her museum."

Good, I thought. This might work.

"Excuse me!" I said loudly, to command the attention of the scientists. In unison, they looked up from their work and stared curiously. A few drifted in from an adjacent room.

"For those I did not meet this morning," I continued, "I'm Dr. Wilson's wife. This is Inspector de Luca of the Naples Fire Department. As I understand it, he needs to conduct an inspection as some kind of post-earthquake measure?" I looked at de Luca, faking timidity. "Is this right?"

He shrugged and looked at me with irritation.

"We must check labs!" he said in a thick Neapolitan accent and then emphasized this with something unintelligible in Italian. After a moment, he returned to English to say, "Go, go!" He waved his hands as if to shoo the occupants from the lab like flies.

"I'm sorry for the disruption," I said, "but the Inspector needs to do this with no interference. You all have the remainder of the afternoon off. Please wrap up your efforts to the best of your abilities in the next fifteen minutes. I promise that you will have plenty of leeway from Dr. Wilson for lost work."

Two employees grinned at each other and promptly strolled out without a word. The other three exchanged frustrated looks of disbelief. One looked at his watch, rolled his eyes angrily, and threw a rack full of test tubes into the garbage. One began frantically clicking buttons on one of the beautiful new state-of-the-art lab computers. The third continued her pipetting, but at a much expedited pace.

We stepped into the adjacent lab spaces, dismissing the occupants of each. "Thank you for your cooperation," I said to them all and led de Luca into Jeff's office.

"OK, let's get started," I said.

I pulled a file from Jeff's file cabinet and showed de Luca how to scan its contents using the copier/scanner near Jeff's desk. Then I showed him how to send the scanned documents to my e-mail address. I quickly sifted through the file cabinet and generated a pile of work for him, basing the prioritization upon my own rushed assessment of the file names.

I pulled five new memory sticks from my purse, sat down at the desk, and opened Jeff's computer. It only took a moment for me to locate the secret e-mail account I knew would be there. It came up automatically when I opened his web browser. While he clearly needed ready access to the account, he also took the precaution of keeping it out of the computer systems he frequently used in San Diego. It took two tries to get the password. It was not HER2 as I had expected. The password was Katrina.

My heart was thumping as I scanned through the messages in the inbox of an e-mail account deliberately not loaded onto Jeff's iPhone. There were many, many messages from aiacovani@gmail.com. Curiosity overcame me, and I clicked on one of the recent ones. It was all business.

I memorized his username and then continued with the task I had come there to do. I clicked quickly and efficiently through Jeff's desktop and hard drive and began copying every file I could find.

Two hours later, both Aldo de Luca and I had made considerable progress, but many files and documents remained to be copied. Nonetheless, it was now 4:00 p.m., and I needed to move on.

"OK," I said. "That's it."

"That's all?" he asked, shocked that fifty thousand euros had been so easy to earn.

"That's all," I reiterated. "Just, please, look around the lab and make sure we are alone before we leave."

He did as instructed and then returned to assure me the coast was clear. I tucked the memory sticks back into my purse, and we cautiously exited the office.

As we passed back through the facility, I found a few notebooks and flipped through their contents. For a moment, I considered taking them. But I knew that they were still needed by the scientists.

I poked around through the lab for a few more minutes before leaving. Because I knew that I would not be returning again.

As we passed through the underground tunnel toward the chapel above us, I chose my words carefully. "I know you can read people. Eerily well. So I will ask you honestly: Do you trust me?"

"Depends," de Luca answered. "What do you want me to trust you with?"

"The one hundred thousand euros I owe you."

"Go on," he said.

"I want to know if you believe I am good for it." He did not respond, so I explained further, "I want to know if you will believe me when I say that I simply can't give it to you immediately. I need all of my liquid assets for myself right now. But I promise that within a matter of days, if I'm still alive, I will set up an account for you and wire the money there."

"And if you're not alive?"

I had been expecting the question, but I still had no answer. We emerged from the tunnel and paused to allow our eyes to adjust to the light in the underground chamber of Cappella Sansevero. De Luca gazed for a moment at the anatomical model of the pregnant female, apparently deep in thought. Then he looked into my eyes briefly before he continued walking.

We both remained silent as we passed up the staircase into the chapel, beyond The Dead Christ, and through the front doors into the street. I was speechless, and he was evidently waiting for an answer to his question. When he changed the subject, I knew my silence had answered the question for him. He knew I had no idea how to pay him in the event of my untimely death. He also knew this was a strong possibility.

"Where are you going?" he asked, and I knew lying to him would be a mistake.

"Egypt."

"Why?"

"Because I have just become a fugitive. I need to get out of Italy."

De Luca stared without speaking, waiting for the rest of the story.

"And because... because that's where I'm going to find something I need to save my daughter's life."

We stood at a crosswalk in the street next to the chapel. De Luca looked me up and down for a moment in silence. When he finally spoke, I realized that I truly had no idea how to read people. I would never have predicted his response at that moment.

"Buona fortuna," he said, and he turned and walked away.

I watched Aldo de Luca go, and as the distance between us grew my stare in his direction became increasingly absent. I wondered if I was making the right move.

As if to answer, the familiar tri-tone of a new text message rang through from my purse. I reached inside and extracted Jeff's iPhone. On it was a text message from John.

Please hurry. The first patient just died.

And so I have come to Egypt.

I suppose that, subconsciously, I had known all along that my quest would bring me here. Two Muslim women on a Naples bus juxtaposed incongruously with a nasty bottle of Naples tap water had been the force that channeled me, like the flow through a Roman aqueduct. But in retrospect, I had actually learned two days earlier that Egypt, not Italy, was where I would find the nardo.

This answer was presented to me in Pompeii, and in Naples. It had come to me in so many ways that I could not believe I had missed it.

How did I miss it?

As I stood in the garden at the House of the Faun, how did I not see it?

Now, it was so obvious.

The last time Katrina Stone was seen, she was entering the Arab Republic of Egypt through Cairo International Airport. After that, there was just another woman in a niqab.

For her actual beauty, it is said, was not in itself so remarkable that none could be compared with her... but the contact of her presence, if you lived with her, was irresistible... something bewitching. It was a pleasure merely to hear the sound of her voice, with which, like an instrument of many strings, she could pass from one language to another; so that there were few of the barbarian nations that she answered by an interpreter; to most of them she spoke herself.

-Lives of the Noble Grecians and Romans Plutarch (ca. 46120 CE) If one tries to navigate unknown waters, one runs the risk of shipwreck.

-Ancient Egyptian proverb

Chapter Eighteen.

Passing through security in Naples was the most terrifying moment of my life. And when I arrived in Egypt, I held my breath at passport control and jumped when I heard the loud strike of the entrance stamp. I approached the customs kiosk wondering if I was charging head-on into a Middle Eastern prison.

At a cash machine in the Cairo airport terminal, I drained my bank accounts, taking a moment to study the large wad of Egyptian pounds before dispersing it into various locations in my pockets and bags. I buried my passport, my credit cards, and every other form of personal identification in my possession within the depths of my luggage. Then I shut off both iPhones, with their GPS tracking features, and buried them in my luggage as well. With that, I erased my own existence.

Following the example first set two millennia ago by Cleopatra, I began creating a new identity. Where Katrina Stone had been, a new, anonymous woman began to emerge.

I inquired at an information booth for transportation to Alexandria. The lady at the booth advised me kindly and in good English that it was too late in the night to travel to Alexandria. In the morning, I could fly or take a bus from the airport or a train from the Ramses station downtown. I asked if there were hotels near the airport.

"Of course," she said. "The Cairo Traveler's Inn is just next to the airport. Would you like me to help you reserve a room?

"No, thank you," I said and smiled politely as I collected my luggage and stepped away. Because I knew that to assist me she would need my passport.

I gathered a few tourist pamphlets and maps of Cairo and stepped outside. The automatic doors had not yet closed behind me when I was assaulted by stifling heat and at least a dozen cab drivers. I struggled to think through the avalanche of broken English pelting me.

"Where you going?"

"Where you from?"

"Which hotel?"

"English?"

"American?"

"Cairo Traveler's Inn," I said, and the taxi drivers universally lost interest. They were looking for a fare into downtown.

Only one driver stayed with me. "Fifty pound," he said, and I was sure it was a considerable rip-off.

"I will give you one hundred," I told him. "But you have to wait outside for me. Do you understand?"

"Mesh mushkela!" the driver said enthusiastically, and then, "No problem!" But I was not convinced.

Oh... my... God...

Whatever chaos I had experienced in Naples traffic paled in comparison to Cairo. It was now the middle of the night, yet my taxi pulled out into traffic that was unlike any rush hour I had ever seen.

The street was about two lanes wide, but four to five cars traveled abreast at any given time. They traveled bumper-to-bumper at top speed, screeching, honking, and weaving around each other like bleating goats in a panicked herd. My taxi swerved between two cars that were not occupying any lanes I could identify, and we passed into an intersection at which eight different streets converged.

My stomach lurched. Oh, no, not again, I thought, as the inevitable motion sickness hit me. But then, we arrived.

After a five minute language struggle, I had to place my bags back into his cab to make the taxi driver understand that I wished for him to wait for me. With that hurdle behind me at last, I stepped inside the hotel.

"Hello," I said at the reception desk, as sweetly as I could. "I am looking for a room." I extracted a handful of cash from my pocket.

"Passport, please," the attendant said and held out his hand.

"I'm sorry," I said. "I have lost my passport traveling. I was planning to go to the embassy tomorrow."

"Driver license," he said.

I grimaced apologetically. "I'm afraid I lost all of my identification." I began rifling through the money and then extending it toward him with no attempt at subtlety.

"I am sorry, madam," he said without a glance at the cash. "We have no rooms."

It took several tries and significant downgrading of standards before I found a hotel with rooms available for a woman with money but no identification. It was in a dark alley in downtown Cairo. The staff spoke virtually no English. As I looked around the lobby, and then my room, I wondered if perhaps I should have slept at the airport.

That night, I became my dead husband.

I dropped my suitcases off in my filthy hotel room and stepped out. Now reluctant to turn on my phones for fear of being tracked, I found an Internet cafe just a few doors down from my hotel.

I first went into my own e-mail account and handled the pressing business from my lab in San Diego, replying to a selection of correspondence from colleagues and employees. Then I logged off and entered Jeff's e-mail account, from which I did the same.

There were two new e-mails from John. Both asked why Jeff had not been responding to his text messages and phone calls. The second message ended with: I have test results. Call me.

I stared at the message for a few moments, and it occurred to me that my suspicions of John were off base. At the very least, he had not killed my husband-John had no idea Jeff was dead.

Unless the texts and e-mails are a cover, my forever skeptical mind prodded me.

I clicked the "reply" button and stared at the blinking cursor for a few moments longer. Then I typed: What can you tell me about the dead patient? Autopsy? I sent the e-mail.

I finally went into Jeff's other e-mail account-the secret one he had created without my knowledge. I located the names and contact info of a number of scientists employed by Jeff to operate a new chemical biology facility in Naples. I began scanning through the correspondence between Jeff and a chemist who appeared to have the highest position.

His name was Romano Moretti. It seemed familiar. Although not a chemist myself, I was reasonably certain that Moretti was somewhat famous among his peers. I clicked into PubMed-the international database for peer-reviewed scientific publications-and searched for him. An extensive publication record appeared. I skimmed through a few of Moretti's most recent papers and saw that the majority were in the world's top chemistry journals. This was the man Jeff had hired to run the chemistry lab in Naples in his absence. Jeff had selected the best.

I e-mailed Moretti from Jeff's account. I instructed him to begin processing the mounds of samples that had appeared in the lab the previous day, although I had seen for myself that the work had already been initiated.

I paused as a thought struck me, Was the whole day I spent collecting those samples a wild goose chase?

I was sure I would find the nardo in Egypt, if at all. But the environment in which the isotope was produced-the soil, the air, the elements-could have been Italian. Or they could have been Egyptian. Or even Nepalese, had the nardo originated in the Himalayas. I shrugged, sighed wearily, and pressed the "send" key for the e-mail.