Though by comparison with these problems it was a minor complaint, I continued to be thwarted by the water mill. Aratus had no solution. I even invited Meto to help, but perhaps he detected the suppressed scepticism in my voice, for he exhibited an extreme disinterest. The failure of the mill would not have mattered so much if I had not begun the labour in memory of Lucius Claudius. Nor did it help that I had told Publius Claudius across the stream about it and had even invited him to share in its use. I hated to think of the wicked fool laughing smugly at my failure and passing the tale to his cousins Manius and Gnaeus behind my back.

On the morning of the Ides of September, I took a trip into the nearest village. We were constructing a new stone wall along one side of the stable, and I needed to hire a few extra labourers for the day. There was a market in the village where this could be done. I might have sent Aratus alone on the errand, but given the ugly events that had transpired on the farm that summer, I wanted to see for myself where any hired labourers came from and look them over before letting them on my property.

Aratus and I left on horseback early in the morning and returned a few hours later, leading a band of six workers on foot. They were slaves, but not shackled; these were trusted men, lent out by their masters for a fee. I would have preferred to use freedmen, but the man who ran the labour market in the village said that they had grown scarce in recent years. In hard times freedmen tend to give up the one thing they own, selling themselves back into slavery just to keep from starving.

As we turned off the Cassian Way, Aratus rode up beside me. 'Visitors, Master,' he said.

Sure enough, two strange horses stood tethered outside the stable, a dot of black and a dot of white against the wall. I left the slaves to Aratus and rode ahead. Meto had been in charge of the farm in my absence; I had made a point of conferring the responsibility on him, thinking it might help salve his pride. But when I reached the house he was not in sight, nor did he come when I called. The slave who was on watch — since the finding of Forfex, I had always kept watchers posted — scurried across the pitched roof of the stable and jumped to the ground.

'Where is Meto?’

'Down at the mill, Master.'

'The visitors?'

'Also down at the mill.'

'Only two?'

He nodded.

I rode at a gallop but slowed as I approached the mill. I dismounted and let the horse wander down to the streambed in search of tender grass and any pools of water that might be found among the dry stones and caked mud. As I approached, I heard a familiar voice from within.

'Then the problem must be here. Well, it's obvious these two gears were never meant to mesh — like trying to mate an ass and a goat.'

This was followed by good-natured laughter — Meto, laughing with more genuine enthusiasm than I had heard from him in many days, and someone else. I stepped into the doorway and saw Tongilius leaning against one wall with his arms crossed. His tunic was dusty and his hair windswept from riding. Meto stood nearby. They were both looking towards Catilina, who crouched among the great wooden wheels and axles. As I entered they all looked towards me.

'Gordianus!' said Catilina. ‘What a piece of work you've created! You thought up this design yourself?'

'With some help from Aratus.'

'Amazing! You're already known for cleverness; let no man say you lack ambition as well. I thought all the engineers were busy building catapults and siege towers for the legions, or else constructing bridges and aqueducts for the Senate. You have quite a talent. Who taught you?'

'Books and common sense. Having eyes and ears also helps. But not enough, I'm afraid. The mill doesn't work.'

'Ah, but it will. There's only one thing stopping it.' '"What do you mean?'

'Look here, at this shaft. It's exactly wrong.'

'What do you mean?' I found myself irritated at his self-assurance, but at the same time I had a glimmering that he knew what he was talking about.

'It should originate there,' he said, pointing, 'and be precisely perpendicular to its present arrangement.'

'But that would mean moving everything else around, changing the structure completely,' I said, hardly believing the solution could be so easy.

'Not at all. The two gears will meet side by side rather than at right angles. As it's now arranged, the mechanism must tear itself apart within a revolution. But with that single change—'

'By Hercules!' I tried not to look a fool, agape at how simple it was. He was absolutely right, without a doubt. 'Why could I not see what was before me?'

Catilina shrugged and laid his hand on my shoulder. His hair was windswept like Tongilius's, and his face was ruddy from riding. He looked half his age, happy and sure of himself, not at all like a skulking conspirator. 'You created the mill from scratch, and your head is cluttered with all the multitude of choices that went into its design; amid so many others, the single small detail that keeps it from working is invisible to you. I, on the other hand, came upon the design in its elegant entirety, and to me the one thing wrong with its perfection is glaringly obvious. You see, Gordianus, sometimes a fresh perspective can be of immeasurable help to a man. You're not the only one who needs that from time to time.' His voice lent a certain gravity to these final words, and he gave me a significant look as he gave my shoulder a squeeze before releasing it.

I contemplated the gears, trying to convince myself to accept the simplicity of Catilina's solution. Was his deduction as unremarkable and logical as his unassuming explanation made it sound, or was he a genius? How could he see in a moment an answer that had been perplexing me for months? I was at the same time irritated, impressed, elated, and still dubious.

'You've been riding,' I said absently. 'Surely not all the way from Rome this morning?’

'No, from up north,' said Tongilius. Catilina had been conferring with his general Manlius and the Sullan veterans up in Faesulae, I thought.

'Your invitation to me still stands, doesn't it?' interjected Catilina with a smile. 'Marcus Caelius led me to dunk so.'

I took a quick breath and pretended to examine the gears again so that there would be an excuse for the hollowness in my voice. 'Yes. Of course.'

'Ah, good. You'd be surprised, or perhaps not, at how many of my friends and colleagues suddenly have no room for me under their roofs after my latest disaster at the polls. But then other friends appear, to make up the balance.'

Catilina and Tonguius retired to the house to rest and change their clothes. I was too excited at the prospect of finally completing the mill to join them. Instead of building the new wall at the stable, I set the hired labourers to work realigning the gears. We worked into the night. Bethesda sent Diana to call me to dinner, but I told her to send down some bread and cheese instead.

Eventually the new arrangement of gears was set in place. In the absence of a rushing stream, slaves pushed the paddle wheel. Within the mill the mechanism shuddered and began to turn. The shafts revolved; the teeth fitted and meshed; the grinding wheel turned for one revolution, and another, and another, without mishap.

Small adjustments would be necessary, the housing would have to be completed, and actual use would no doubt suggest improvements, but for all practical purposes the mill was a success.

This moment filled me with a greater sense of achievement than I could have anticipated. Aratus wore such a smile as I had never seen on his face before. Even Meto dropped his sullen frown and seemed to share in my excitement. Catilina should have been with me. I looked towards the house, at the darkened windows, and wondered again at the simplicity of his genius.