The crowd began to move. How this movement began, I never quite understood. I saw no signal from the tribunes on the stage. I heard no shout from the crowd, urging everyone to head for the house of Lepidus. Perhaps if I had been on my rooftop watching instead of in the thick of things, I could have seen and understood the dynamics of the mob – or perhaps not. One might as easily comprehend the uncanny unison of a swarm of bees in flight.

However it happened, the crowd became a mob, and the mob began to move as a single body towards the Palatine. Eco and I moved along with it for a while, unable to separate ourselves, like flotsam on a current. I was jostled and poked and pushed forwards against my will. I gritted my teeth and grunted. But the same experience that I found so unpleasant seemed to invigorate many of those around me, who grinned and made giddy whoops of excitement as if they had drunk too much wine.

Little by little we worked our way sideways through the press of the crowd until we reached the edge and were able to drop back. Even Eco seemed intoxicated by the excitement. "What's wrong, Papa?" he said, smiling and catching his breath. "Don't you want to join the march on the interrex's house?"

"Don't be funny, Eco. There's no telling what will happen. I'm going home. So should you."

I spent that afternoon on my rooftop, anxiously looking for signs of fire or smoke. I saw none, but heard the clattering echoes of some kind of battle taking place in the direction of Lepidus's house.

A sharp wind began to gust from the north, followed by dark clouds. As the first cold raindrops pelted my face, Bethesda appeared in the garden.

"Come down from there!" she demanded, her hands on her hips.

I obeyed. But halfway down the ladder I turned to stone, as did everything around me. A bolt of lightning opened the sky. Jupiter blinked, as the augurs say. The blinding flash of bone-white light was followed by a crack of thunder so loud that the earth itself seemed to flinch. Rain swept across the garden. I hurried down the ladder, shivering, and told Belbo to light the brazier in my study.

I hardly had a chance to warm my hands over the flames before Belbo was back, announcing a visitor. "The same as before," he said. "Cicero's man."

"Tiro?"

Belbo nodded.

"Well, show him in."

"What about his bodyguards?"

"They can stay outside in the rain."

A moment later Tiro stepped into the room, pushing the hood back from his face. His heavy woollen cloak was wet. He covered his mouth and coughed.

"Cicero shouldn't send you out in the rain, Tiro. He should consider your health."

"It's only a short walk. Besides, he thinks you're fond of me."

"And that I might not come if he sent someone else to fetch me?"

Tiro smiled. "Will you come?"

"Shouldn't you and I have a brief polite conversation about the weather first?"

"Thunder and lightning," said Tiro, rolling his eyes skyward. "Omens and portents."

"If you believe in that sort of thing." "Doesn't everybody?"

"Don't be disingenuous, Tiro. It doesn't suit you. Just because your master – your former master, I mean – pretends to go along with such superstitious ideas for the sake of politics…" "You really despise Cicero, don't you?"

I sighed. "No more or less than I despise all the rest of his kind, I suppose." "His kind?" "Politicians."

"No, I think you despise him more than the rest. Because once upon a time you thought he was different somehow, and then he disappointed you."

"Perhaps."

"Whereas you expect only the worst from the rest of them, so they've never let you down." I shrugged.

"But isn't it really only your own false expectations that have let you down, Gordianus? Do you think a man can cross a muddy street without getting his feet dirty? Cicero can't walk on air. No one can."

"Cicero doesn't just cross the muddy street, Tiro. He stoops down and flings handfuls of mud at anybody in his way. He sticks out his foot and trips people – and claps when they fall on their faces! Then he washes his hands at the nearest fountain and blithely pretends they were never dirty."

Tiro gave me a grudging smile. "Cicero can be a bit self-righteous."

"Smug is more like it."

"Yes. Well, I try to tone down those parts in his speeches. But it's a funny thing. People may say that modesty is a virtue, but they respect a man who sings his own praises. They think if he's vain, he must have a reason. And when such a bright fellow starts slinging mud, they pay attention. They figure he must have a good reason for doing that, too."

"You don't have to convince me that Cicero knows how to manipulate an audience."

"Gordianus, these are merely questions of style, not content. Certain things about Cicero rub you the wrong way. Don't you think I sometimes tire of his manner, spending so many hours of the day in his company? He can drive me mad! And yet I've never met a more admirable or honourable man in all my life. Fundamentally, you and Cicero are on the same side -"

"Tiro, you needn't try to convince me to come along with you. I've only been waiting for a break in our conversation to send Belbo after my cloak. But look, here he is, already anticipating my needs." Belbo put the cloak over my shoulders. I pulled it around me. "The weather has turned colder."

"Still, let's hope this rain keeps up," said Tiro. "It makes it harder to start fires. Keeps the flames from spreading. There, we've talked about the weather. Shall we be going?"

I found Cicero in his study, deep in conversation with Marcus Caelius.

Cicero looked up and saw me scanning the room. "Milo isn't here," he said. "He's returned to his own house. A show of self-confidence. After all, what does Milo have to fear in his own home, when the people of Rome love him so?"

"Do they?"

"How can they not, after the favour he's done them, ridding the world of that appalling scoundrel? 'He trapped the tyrant in iron bands.."

" 'And slew him with his own bare hands’ " I said, finishing the quotation from Ennius. "Well, did he?" "Did he what?"

"Did Milo slay Clodius with his own bare hands?" I remembered the marks I had seen on Clodius's throat. Something had been twisted around his neck before he died, either to restrain him, or to choke him, or to drag him.

Cicero shrugged. "I wasn't there to see. But the image appeals to me. Like his namesake, the fabled wrestler of Croton, Milo is a strong fellow. I suppose he could strangle a man to death. What do you think, Caelius?"

Caelius looked thoughtful. "Strangulation? It might make people forget the blood… take their minds off those gaping wounds. The idea of Clodius being strangled – I like it. It's cleaner, less gory. Thinking about knives sets people's teeth on edge. Strangulation is more manly, more heroic. It suggests killing an animal barehanded. It equates Clodius with a wild beast. Best to skirt such graphic details, really, but if we must discuss the actual where and how of the murder-"

"I didn't come here to listen to two orators toss ideas in the air," I said.

Caelius smiled. "But how else can we see which ideas float, and which ones fall like stones?"

"You can do that after I leave."

Tiro made a face of disapproval at my rudeness.

"Why did you agree to come, Gordianus?" said Cicero. "I thought perhaps Tiro had converted you with his eloquence."

"Converted me? But I thought you said we were already in the same camp, Cicero."

"We are. You just don't realize it yet." He laced his fingers behind his head and smiled.

"Don't be so smug, Cicero. You asked me to come. Here I am. Why did I come?" I walked to the brazier and spread my hands over the flames. "Because it's a cold night in Rome, and dark outside, like everyone else I'm craving warmth and light. Especially light. My reasons for coming are entirely selfish. I want more illumination on the path ahead, any glimmer to show the way. Knowledge is a fire. It burns high in this house. But right now it seems to be putting out a great deal more smoke than light"