“But you’ve left out one of the Wonders,” I said.

“Ah, yes, the Colossus of Rhodes—which was not completed until some thirty years after Alexander died. Obviously, Alexander never saw it—but that leads to the next proposition of my theory: Alexander himself did not draw up the final list, but assigned the task to someone else. Perhaps it was his close friend, the historian Aristobulus, or Callisthenes, the nephew of Aristotle, or—this is my guess—his comrade Ptolemy, who was later to become King of Egypt and had his own stake in preserving the mystique of Alexander and the legacy of his world empire. Ptolemy of course had all the resources of the Library and its scholars at his disposal—and it was in the Library, I believe, that the very first compendium of the Seven Wonders was created. I believe this was considerably more than a mere list, but included a detailed history and description of each Wonder. This book may yet be discovered in the archives, with the name of its author or authors appended to it. At the time this compendium was written, the Colossus would have been brand-new, a sensation that everyone was talking about, so it was included alongside the more venerable Wonders to demonstrate that mankind was still progressing and capable of creating new marvels.”

“I think the Pharos is a greater achievement than the Colossus,” I said. “Why didn’t Ptolemy’s scholars put it on the list instead?”

“Because the list predated the completion of the Pharos,” explained Antipater. “The lighthouse was still being built as the list was drawn up—and even scholars eager to flatter King Ptolemy could not have justified comparing an unfinished building to the Temple of Artemis or the Great Pyramid.”

“But now the Pharos has been standing for almost two hundred years,” I said, “while the wonders of Babylon are in ruins. Perhaps the Hanging Gardens or the Walls of Babylon should be removed from the list, and the Pharos put in their place.”

Isidorus laughed. “What a brash young man you are, Gordianus, to propose such an idea.”

“Do you not like it?”

“I love it—but I’m afraid my colleagues at the birdcage of the Muses are so used to scratching out the same old things, not one of them would be bold enough to propose such an innovation. I fear they will resist the theory of Zoticus, as well, unless he can produce the original list. But as yet, this discovery eludes you?”

Antipater nodded. “I’ve found a number of citations that refer to such a document, but not the document itself. But soon—very soon—I feel sure that I’ll lay my hands on it. It’s probably moldering away in a stack of uncatalogued papyri, or inadvertently rolled up inside another scroll that has nothing to do with the Seven Wonders.”

“Books in the Library can be quite elusive. You may have set yourself a task of many months, Zoticus my friend.”

“Then I must pray to Zeus the Savior that I will have that much longer to live,” said Antipater.

“I will say a prayer for that, as well,” said Isidorus.

“And so will I!” I cried. I had grown so used to Antipater’s company that it was unthinkable that anything should happen to him, or that I should be left alone without him in the vast, teeming city founded by Alexander.

*   *   *

That night—thanks to my father’s letter, or something disagreeable in the fish stew—I was plagued by terrible dreams. All was a confusion of screaming and bloodshed. My father figured somehow in these nightmares, and Rome itself was swept by fire. The Pharos was transported to the summit of the Capitoline Hill, a finger of stone soaring to an impossible height, from which it sent out a beacon not to sailors, but to Rome’s enemies, guiding them from all over Italy to the city they longed to destroy.

I tossed and turned and struggled to wake from these nightmares. Like a man submerged in deep water but able to glimpse pale daylight, gradually, fitfully I rose toward consciousness. I opened my eyes to the soft light of dawn. The sheet twisted around me was soaked with sweat.

I heard familiar voices from the room beyond—Antipater and our host chatting amiably as they prepared to head out for the day. Their conversation was muted and the words were indistinct, until one of them opened the front door, and Isidorus, raising his voice a bit, said, “And don’t forget to bring your new stylus this morning, Antipater!”

A moment later the door was slammed shut, and silence followed.

I shut my eyes and lay still, exhausted by my nightmares. I was nearly asleep again, when suddenly I bolted upright. Had I heard what I thought I heard, or only dreamed it?

Not “Zoticus,” but “Antipater”—Isidorus had called him by his true name.

What did it mean?

*   *   *

As I strolled around Alexandria that day, I should have been in a good mood, for I was no longer a pauper but had some coins on my person, thanks to the funds from my father. With a bit of money, there were endless things to do in Alexandria.

Instead, I found myself walking in circles. That single utterance by Isidorus kept echoing in my head, nagging at me.

There would be a perfectly innocent explanation, I told myself. Antipater had come to trust Isidorus, and so had revealed to him his true identity. That was Antipater’s choice, and none of my business. But why, then, had Isidorus continued to address him at dinner as Zoticus?

Because the slave was present, I told myself. Yes, that was it. The woman serving dinner was not to know who Antipater was. But why hadn’t Antipater informed me of his decision to reveal himself to our host? Ah, well, he was an old fellow and he simply forgot. But even as this thought came to me, I knew it was a lie. Antipater’s mind was as keen as ever, and he never did anything without a purpose. Some sort of relationship existed between him and our host, and I was being kept in the dark about it.

Why?

I found myself in the Rhakotis district, the oldest part of the city. Rhakotis had been a settlement in Homer’s time; its narrow, winding streets predated the grid laid down by Alexander’s new city. With its shabby tenements, gambling dens, and seedy taverns, Rhakotis reminded me of the Subura in Rome.

Passing through a particularly tawdry part of Rhakotis, I passed a building that was clearly a brothel, to judge by the attitude of the women who stood at the upper-story windows, flaunting their naked breasts and looking bored. A man stepped out of the front door. He looked this way and that, but took no notice of me.

A lightning bolt of recognition struck me, followed by a quiver of doubt. Could the man possibly be who I thought he was?

He was burly and blond, with a neatly trimmed beard, and his clothing was Greek. In a teeming metropolis like Alexandria, there were countless specimens almost exactly like him—and yet, something about the arrogant tilt of his head and the truculent way he held himself as he turned and walked quickly away, clenching his fists, convinced me that he was none other than the murderer from Olympia.

I remembered everything about him in a flash: standing behind me at the Temple of Zeus he had loudly voiced anti-Roman sentiments; later that night I had overheard him speaking to an unknown conspirator—a fellow agent for Mithridates—in the tent of our host; and the next day he had used a snake to poison the Cynic, Simmius of Sidon, and then, in the ensuing confusion, had vanished into thin air, not to be seen again—until now.

They had a saying in Alexandria: “Stay here long enough, and every traveler in the world will cross your path.” Apparently it was true.

I quickened my stride to match his. Keeping what I hoped was a safe distance, I followed the murderer.

He apparently had several calls to make, for repeatedly I saw him disappear into a tenement or private dwelling, stay for a short while, and then reappear, always pausing to peer suspiciously up and down the street before proceeding. I had to call upon all the skills my father had taught me to shadow him without being spotted.