Some tenement landlords post a slave at the front door to keep out thieves and troublemakers, but there was no slave at the entrance, and when I tested the door I found it had no lock, either. It was hard to imagine anything inside such a building to tempt a burglar.

"Mopsus," I said, "I want you to stand across the street while Androcles and I go inside. Try not to look like a runaway slave up to no good."

"I'll stand watch!" said Mopsus eagerly. "If anybody dangerous-looking goes in after you, I'll run up and tell you."

I shook my head. "No, Mopsus. I imagine any number of dangerous-looking men, and women for that matter, are likely to live in this building; this is a dangerous neighborhood. But tenement dwellers must come and go. How could you possibly know who has legitimate business in this building and who does not?"

Mopsus scratched his head.

"And if some assassin were to enter this building, intending to do me harm, how could you get past him to warn me?"

Mopsus frowned. Androcles covered his mouth, laughing at his older brother's consternation. I put my hands on their shoulders and walked them both across the street.

"Mopsus, I want you to stand precisely here. Now, do you see that corner window up on the fourth floor? The one with the shutters intact? I want you to watch that window. In a moment, if all goes well, I'll open those shutters and give you a wave. Don't wave back. But keep watching the window. If something should go wrong, you'll see me or Androcles at that window again. If we scream for help, I want you to run to Eco's house and tell him. Do you think you could find your way to Eco's house from here? It's just up the Esquiline Hill."

Mopsus nodded mutely, his eyes wide at the gravity of his post.

"Good. Now keep your eyes on that window!"

I crossed the street with Androcles and entered the tenement. The narrow hallway was deserted and, except for the crying baby, quiet. The tenants, like most people in Rome, were out in the markets searching for the necessities of life, which became harder to find each day.

A stairway at one end of the hall led to the upper floors. I ascended and Androcles followed. "We shall be visiting a secret room, Androcles, where we have no business being. I shall need you to keep watch in the hall outside."

He mimicked his brother's grave nod.

"And I may need you for something even more important."

"What, Master?"

"I shall be searching for something. It may be well hidden and hard to reach. A pair of tiny hands could turn out to be very useful."

"My hands are smaller than Mopsus's," he boasted, holding them up for me to see.

"So they are."

We reached the landing of the third floor. The sound of the crying baby receded. The smell of cabbage grew stronger, mingled now with other smells- onions, perfume, lamp oil, stale urine. What had the daughter of Titus Aemilius thought of such a place?

We came to the top floor. The hallway was empty and dim. I motioned to Androcles to tread quietly.

I located the loose floorboard, just where Aemilia had described it. Wedged in a narrow space beneath was the key. It was not one of those stout keys with notches, to be inserted into a lock and given a strong turn, but a thin bronze rod which curved eccentrically this way and that, as if it might have been accidentally bent beneath a wagon wheel. At one end there was a tiny hook.

Finding such a key is only half the trick in using it. The eccentric shape allows it to slip through the equally eccentric passage inside the keyhole. Once through, the hook at the end needs to find the eye it was fashioned for, which, unless the user has used that particular lock before, can require a considerable amount of trial and error.

I replaced the floorboard and stepped to the door. The lock was a bronze box bolted to the wood from inside. In such a neglected, insecure building, the elaborate mechanism seemed conspicuously out of place.

I slipped the key in, twisted it this way and that to negotiate the hole, then tried to imagine in my mind's eye what the hook needed to catch against. Up or down? Farther in or farther out? A jiggle or a twist? I tried various motions, then finally removed the key and started over. Again, I had no luck. My patience nearing an end, I pulled out and tried once more. This time, I seemed to locate a divergent keyhole. The key entered in a different direction. The hook caught on something. I held my breath, turned the key and pulled toward me. The lock gave a satisfying click. The door opened.

Behind me, I heard Androcles release a pent-up breath. I looked over my shoulder and nodded toward the stairs. "Stand watch on the landing," I whispered. "If anyone starts up, come quietly and let me know. Can you do that?"

He nodded and tiptoed toward the stairs.

I stepped inside and pulled the door not quite shut behind me. The room was even darker than the hallway. I found my way to the window at the southwest corner, which was covered with heavy winter drapes, made of a fabric far superior, I wagered, to anything to be found in the other apartments. I pulled them apart and opened the shutters. Above the rooftops, as Aemilia had said, I could see the sacred temples atop the Capitoline Hill. Mopsus stood across the street, leaning against a wall, his arms crossed, idly kicking his heels against the ground. He looked up at the sound of the shutters opening. I waved. He uncrossed his arms and started to wave back, then caught himself. He peered up and down the street, hardening his posture and trying to look formidable. I shook my head. If I had specifically asked him to look like an errant slave bent on getting into mischief, he could not have delivered a better performance.

I turned around and surveyed the room. It was sparsely furnished with a low sleeping couch and a little trunk against one wall. Perhaps it was nothing more than a love nest, after all. Lovers' needs were simple.

Atop the trunk there was a simple oil lamp, a vessel containing spare oil, and a small round mirror. I peered inside the lamp and the vessel and poured oil back and forth between them until I was satisfied that they contained nothing else. The mirror was of solid silver and had no secret parts. I glanced at my reflection. I saw a bearded man with furrowed brow but clear eyes, not yet entirely gray and youthful-looking for his years, a sign of the gods' favor. The fact that it was Aemilia's mirror made me uneasy. I put it aside.

The trunk was not locked. Inside I found a few pieces of clothing- a man's loincloth and tunic, a cloak that might have been worn by either sex. There was also a spare coverlet for the bed. At the very bottom, there was a small dagger. That was all.

The trunk appeared to contain nothing of significance. But remembering that Numerius Pompeius had carried confidential reports in his shoe, I looked at each item again. Satisfied that the dagger had no secret compartments, I used it to cut open the stitches of each garment. I had brought my own knife for the purpose, but this one looked sharper. I found nothing.

I examined the empty trunk. I used the dagger to undo the hinges and cut into the leather. I turned it over and rapped on the bottom, listening for the hollow echo of a hidden compartment. The trunk was nothing more than an ordinary trunk.

I turned my attention to the bed.

It was a fine piece of furniture- like the drapes, surely finer than anything to be found in the humble apartments down the hall or on the floors below. The frame was made entirely of ebony with ornately carved legs. Against the wall, an ebony sideboard inlaid with ivory ran the length of the frame from head to foot. Aemilia would have lain on the inner side, next to the board and the wall; Numerius would have lain on the outside, as men typically do. I once explained to Bethesda that this arrangement was so because the man protects the woman in sleep. She laughed and said it was because men needed to get up and pass water more often during the night.