As Lucius made ready to leave the house – alone, as he always did when he was going to meet his secret lover – he whistled the tune of an old hunting song. Hilarion went about his business.

It was a brisk autumn afternoon. Lucius took a round-about route, occasionally glancing over his shoulder and doubling back. Long ago he had adopted such habits to make sure he was not being followed when he set out for the little house on the Esquiline.

As usually happened when he returned to Roma after an extended stay in the country, he found the city disgustingly dirty and noisy and smelly, full of unhappy and dangerous-looking people – and that was just in the Forum. Once he entered the Subura, he actually felt more relaxed, because, although the streets were more crowded and the people were dirtier, there were not quite so many statues of Domitian everywhere. That was the most unnerving thing about the first day or two back in Roma – the ubiquity of Domitian, Master and God, always watching him.

But even the inescapable images of the emperor could not dampen Lucius’s mood on this day. Perhaps it was the nip of autumn in the brisk air that made Lucius feel half his age. Or perhaps it was the fact that he had not seen Cornelia in so very long – more than two months – and at last they had both found time to meet. He had received her cryptic message at the baths that afternoon, delivered as always by a street urchin selected at random who could not possibly know the identity of the woman who hired him or the meaning of the words he was told to repeat: “Today. An hour before sunset.”

Shops in the better parts of town would already be closed, but many establishments in the Subura stayed open until it was dark, and Lucius had found that the quality of their foodstuffs was often as good as anything to be found in shops on the Aventine that charged four or five times as much. He bought some flatbread with a thick crust, a hard, smoked cheese, a little jar of his favourite garum, and a few other items. There would be wine and olives in the little house on the Esquiline, but no fresh food, and if experience was any guide, they would both have a ravenous appetite later. He left the Subura and ascended the hill, carrying a cloth bag with his provisions and whistling a happy tune.

He stopped whistling when he saw the Praetorians who loitered around the little reservoir called the Lake of Orpheus. The soldiers were armed and in uniform but appeared to be off duty. One of them had climbed amid the bronze statues in the fountain and was leaning against a deer that stood enraptured, ears pricked up to listen to Orpheus play his lyre.

What were Praetorians doing in this mostly residential area, with its mix of elegant homes, like that of Epaphroditus, and more modest but still respectable dwellings, like the little house Lucius kept? The sight of armed men was disturbing. He almost turned back, then thought of Cornelia, patiently waiting for him. He continued up a winding, narrow street. After a sharp turn, he saw the front of his house.

The door was wide open.

He turned around. The soldiers he had seen at the Lake of Orpheus had followed him. The foremost of them looked him in the eye. The man’s expression was dispassionate but determined. With a nod and a slight gesture of his hand, the Praetorian made it clear that Lucius was to enter the house.

He passed through the vestibule and entered into the room beyond. Someone was sitting on the couch where he had expected to find Cornelia. The room was dim; it took his eyes a moment to adjust. The man on the couch was dressed like a member of the imperial court, in a lavishly embroidered robe with long sleeves. He wore a necklace with large pieces of carnelian and a ring of the same red stone on one finger. He turned to face Lucius, but there was a disconcerting blankness about his eyes, which seemed to fix on nothing. His face was gaunt. His skin was pale and mottled.

“Are you Lucius Pinarius?” the man said.

“I am.”

“My name is also Lucius. I am Lucius Valerius Catullus Messalinus. Perhaps you’ve heard of me.”

“Perhaps.”

“Do I hear a quaver in your voice, Lucius Pinarius?”

There appeared to be no one in the room but the two of them. From a shadow on the wall Lucius could see that one of the Praetorians had followed him into the house and was standing in the vestibule.

“Your presence honours me, Catullus.”

Catullus laughed. “How polite you are, Pinarius! Decorum would have me now say something complimentary about your home, but alas, I cannot see it. My other senses are quite sensitive, however. Do I smell, very faintly, a woman’s perfume in this room? Or do I only imagine it?”

“There’s no woman here, Catullus.”

“No? And yet, I can almost feel her presence.”

In the silence that followed, the items in the cloth bag made a slight rustling sound.

“What’s that you carry?” said Catullus.

“Only a bit of food. May I offer you some, Catullus?”

Catullus laughed. “Oh, no, I never eat anything not prepared by my own cook, or that of the emperor, and tasted first by a slave. Such essential precautions are one of the drawbacks of my station in life. I would advise you not to eat any of that food, either.”

“Why not?”

“Why spoil your appetite, when shortly you shall be dining in the House of the Flavians?”

“I will?” Lucius’s voice cracked like that of a boy.

“That’s why I’m here, Lucius Pinarius. To deliver an invitation from our Master and God. You are invited to dine with him. A sedan is waiting outside.”

Lucius swallowed. “I’m not properly dressed. I’ll need to go home first, to change into my best toga-”

“No need. The emperor will provide your clothing.”

“He will?”

“This is to be a special dinner, requiring special dress. You need bring nothing. Shall we be off?”

Lucius looked around the room. Where was Cornelia? Had she arrived before him, seen the Praetorians, and left? Had she not come at all? Or – he could hardly bear the thought – had she been here when Catullus arrived?

Catullus called to the Praetorian, who assisted him as they stepped outside the house. Lucius pulled the door closed and produced his key.

“What are you doing?” said Catullus.

“Locking the door.”

Catullus shrugged. “If you wish.”

It seemed to Lucius that his meaning was clear: there was little need to lock a house to which a man would never return.

He was carried through the streets in a sedan that seated only himself. He made no attempt to converse with Catullus, who had his own sedan and was carried sometimes alongside him, sometimes in front, depending on the width of the street. Lucius found himself thinking of stories he had heard regarding the cruel games Domitian played with his victims, disarming them with gifts and tokens of friendship before subjecting them to hideous tortures. His favourite interrogation technique was to burn the genitals of his victims. His favourite punishment, short of death, was to cut off their hands.

The shortest route to the palace would have taken them close by the Flavian Amphitheatre and the Colossus. Instead, they went through the Forum, passing by the House of the Vestals and the Temple of Vesta. Was this done deliberately to unnerve him? Surely it was, for when they at last ascended the Palatine, the bearers passed directly by Lucius’s house. Catullus had to know exactly where they were; as they passed by the house, his sedan fell back alongside that of Lucius, and Catullus turned turn his head to Lucius and smiled, as if to taunt him with a final glimpse of his home.

The sedans deposited them at one of the entrances to the imperial palace. The reception chamber to which they were led, with its soaring ceiling, was grander than any room Lucius had ever seen before. Even the most ornately decorated temples could not compare with the opulence of the place, which was perhaps best seen at this hour of the day. The last of the fading sunlight from the high windows still lit the far corners, revealing the sheer scale and the astounding attention to detail, while a multitude of newly lit lamps gave a lustrous gleam to the polished surfaces of marble and bronze and caused the monumental statue of Domitian at the centre of the chamber, covered with silver and gold, to sparkle with points of fiery light.