The man came into the room, followed by the other. Now I remembered where I had seen that one. He was the hatchet-faced officer who had shooed me away from the parade ground.

"I am Achillas," said the first man, "Commander of the Royal Army." He wore studded boots and a rich, red tunic. Over that he wore one of those leather strap-harnesses that military men sometimes wear to give the appearance of armor, without having to endure its weight. His hair and beard were trimmed close all around.

"And I'm Memnon, Commander of the Macedonian Barracks," said the other. "We've met." They were both Macedonians, a nation of men who simply use their names, without the of-this-or-that the Greeks delight in so.

"So we have. And what are you two doing here?"

"By whose authority do you investigate?" demanded Achillas.

I was ready for that one.

"The king's," I said, holding out my sealed document. He studied it through slitted eyes.

"That damned, drunken fool," he muttered. Then, to me: "What is your interest in this matter, Roman?"

"Rome is the friend of Egypt," I said, "and we are always pleased to render aid to King Ptolemy, Friend and Ally of the Roman People." I always loved this sort of diplomatic hypocrisy. "I am known in Rome as a skillful investigator of criminal acts, and I am more than happy to place my expertise at the service of the king." I refolded my commission and placed it inside my tunic, leaving my hand there for the nonce. Memnon pushed forward, glaring at me. He wore cuirass and greaves, but no helmet. I was intensely aware of the short sword belted at his side.

"You aren't wanted here, Roman," he growled. "Go back to your embassy and drink and fornicate like the rest of your worthless countrymen. This is Egypt."

At our first encounter we had been on his ground, surrounded by his soldiers. This was different.

"I am in the service not only of the Senate and People of Rome, but of their ally, your king. I believe that I am far more loyal to him than you are."

They always get that look in their eyes when they go for their weapons. With a strangled sound of rage he gripped his sheath with one hand and his hilt with the other. I was ready for that, too.

The blade was halfway out of its sheath when my own hand emerged from my tunic, now gripping my caestus. I fed him a good one, the spikes on the bronze knuckle-bar catching him on the jaw just in front of the ear. He staggered back with a grunt of amazement. I was amazed, too. I had never struck a man with my caestus without knocking him down. So I hit him again, on the same spot. This time he toppled amid a crash of bronze, like those heroes sung of by Homer.

The secretaries and the Librarian wore round-eyed expressions of surprise and fear. Hermes grinned happily, like the bloody-minded little demon that he was. Achillas looked very grave.

"You go too far, Senator," he said.

" I go too far? He attacked a Roman Senator, an ambassador. Kingdoms have been destroyed for that."

He shrugged. "A hundred years ago, perhaps. Not now." Well, that was true enough. With a visible effort, he calmed himself. "This is not a matter worth provoking a diplomatic crisis. You must understand, Senator, that it always vexes us to see Romans come here and assume authority as if by right."

"I quite understand," I said. "But I am here by authority of your king." On the floor, Memnon groaned.

"I had better see him to a physician," Achillas said.

"I recommend Asklepiodes," I said. "He's nearby. Tell him I sent you." He summoned a few slaves and they bore the fallen hero away. I still did not know why the two were there. They had been reluctant to say, and I thought it unwise to press the matter.

I turned back to the Librarian. "Now, you were about to tell me the nature of the missing book, were you not?" I slipped off my caestus and tossed it to Hermes. "Go wash the blood off that," I told him.

"Why: ah: that is:" Eumenes took a deep breath and calmed himself. "Actually, Senator, it is one of the more valuable works in the Library. It was written by Biton and dedicated to King Attalus I of Pergamum more than one hundred years ago."

"And its title?" I asked.

"On Engines of War."

Hermes handed back my caestus as we left the Museum.

"That was as good as an afternoon in the amphitheater," he said. "But that was one tough Greek."

"Not Greek," I corrected. "Macedonian. An altogether tougher breed."

"I knew he was some sort of foreigner. You should have killed him. Now he'll be coming for you." Hermes had a delightfully simple way of looking at things.

"I'll talk to the king. Maybe I can get him posted up the river someplace. I am more concerned about Achillas. He's the ranking man in the royal army. See what you can find out about him."

I do some of my best thinking while walking, and I had much to think about. So, Iphicrates never designed military machines, did he? Obviously, he had been lying. Typical Greek. But I wondered why all the secrecy. It was not as if the activity were unlawful. There had to be more to it.

Before long, we found ourselves in the quarter of the Jews, an odd race with a paucity of gods. Other than that, they were much like other Easterners. Many thought it strange that their god had no image, but until a few centuries ago, there were no statues of Roman gods, either. The early Ptolemies had favored the Jews as a balance against the native Egyptians. There was some sort of ancient antipathy between the two. As a result, Jews had flocked to the city.

The streets were quiet and almost deserted, an odd thing in Alexandria. I asked at one of the open stalls and found that it was a day of religious observance for the Jews, one that they spent at home rather than in a temple. This was commendable piety but boring for the observer.

"There's other places in this city more lively," Hermes said.

"Unquestionably," I answered. "Let's go to the Rakhotis."

The Rakhotis was the Egyptian quarter, the largest in this most cosmopolitan of cities. It was easily the size of the Greek, Macedonian and Jewish quarters combined. In its own way, it was the oddest, to Roman eyes.

The Egyptians are the most ancient of peoples, and so profoundly conservative that they make the most reactionary Romans appear wildly mutable. The common subjects of the Ptolemies are identical to the ones you see painted in the temples of the oldest Pharaohs. They are short, sturdily built people, dark of skin, although not as dark as Nubians. The usual garment of the men is a kilt of white linen, and most wear short, square-cut black wigs. They rim their eyes with kohl for its supposed beneficial effects, believing that it protects the eyes. The old Egyptian nobility, of whom there are still a few specimens here and there, is of a different race, taller and fairer, although darker than Greeks or Italians. Their language is spoken nowhere outside Egypt.

To see them now makes it difficult for one to believe that these were the people who built the mind-stunning pyramids, but then the Greeks of today aren't much like the heroes of Homer, or even like their more recent ancestors of the Persian wars. The Egyptians take their religion very seriously, despite having some of the most supremely silly-looking gods in the world. Everybody thinks the animal-headed gods are hilarious, but my personal favorite is the one who is depicted dead and wrapped up like a mummy except for his face but who stands upright with an erect penis protruding from his wrappings.

In the Rakhotis we found the usual uproarious street scene, with hawkers plying their wares, animals being led to the markets, and the endless religious processions that are an inescapable part of Egyptian life. Here I was not simply sightseeing. I had a specific destination, but I didn't want to look as if I were investigating in this district.