‘It’s been a long winter -‘ Mario said.

‘Too long,’ put in Ezio.

‘- but now all is settled,’ continued his uncle. ‘And I would remind you that meticulous preparation accounts for most victories. Now, pay attention! I have a friend in Florence who has arranged a secure lodging for you not far from her own house.’

‘Who is she, Uncle?’

Mario looked furtive. ‘Her name is of no consequence to you, but you have my word that you can trust her as much as you would trust me. In any case she is presently away from the town. If you have need of help, get in touch with your old housekeeper, Annetta, whose address has not changed and who now works for the Medici, but it would be best if as few people as possible in Florence knew of your presence there. There is, however, one person you must contact, though he isn’t easy to reach. I’ve written his name down here. You must ask around for him discreetly. Try asking your scientific friend while you’re showing him the Codex page, but don’t let him know too much, for his own good! And here, by the way, is the address of your lodgings.’ He handed Ezio two slips of paper and a bulging leather pouch. ‘And one hundred florins to get you started, and your travelling papers, which you will find in order. The best news of all is that you may set off tomorrow!’

Ezio used the short time left to ride to the convent to take his leave of his mother and sister, to pack all his essential clothing and equipment, and to say goodbye to his uncle and the men and women of the town who had been his companions and allies for so long. But it was with a joyful and determined heart that he saddled his horse and rode forth from the castle gates at dawn the following morning. It was a long but uneventful day’s ride, and by dinner-time he was settled in his new quarters and ready to re-acquaint himself with the city which had been his home all his life, but which he had not seen for so long. But this wasn’t a sentimental return, and once he had found his feet again, and permitted himself one sad walk past the façade of his old family home, he made his way straight to Leonardo da Vinci’s workshop, not forgetting to take Vieri de’ Pazzi’s page of the Codex with him.

Leonardo had expanded into the property to the left of his own since Ezio had gone away, a vast warehouse with ample room for the physical results of the artist’s imaginings to take shape. Two long trestle tables ran from one end of the place to the other, lit by oil-lamps and by windows set high in the walls – Leonardo had no need of prying eyes. On the tables, hanging from the walls, and scattered, partly assembled, in the middle of the room, were a confusing number of devices, machines and bits of engineering equipment, and pinned to the walls were hundreds of drawings and sketches. Among this pandemonium of creativity, half a dozen assistants busied and scuttled, overseen by the slightly older, but no less attractive, Agniolo and Innocento. Here, there was a model of a wagon, except that it was round, bristled with weapons, and was covered with an armoured canopy in the shape of a raised cooking pot lid, at the top of which was a hole through which a man might stick his head to ascertain what direction the machine was going in. There, the drawing of a boat in the shape of a shark but with an odd tower on its back. More oddly still, it looked from the drawing as if the boat were sailing underwater. Maps, anatomical sketches showing everything from the working of the eye, to coitus, to the embryo in the womb – and many others which it was beyond Ezio’s imagination to decipher – crowded all available wall-space, and the samples and clutter piled on the tables reminded Ezio of the organized chaos he remembered from his last visit here, but multiplied one hundredfold. There were precisely figured images of animals, from the familiar to the supernatural, and designs for everything from water-pumps to defensive walls.

But what caught Ezio’s eye most was hanging low from the ceiling. He had seen a version of it before, he remembered, as a smallish model, but this looked like a half-scale mock-up of what might one day be a real machine. It still looked like the skeleton of a bat, and some kind of durable animal skin had been stretched tightly over the frames of two wooden projections. Nearby was an easel with some paperwork attached to it. Among the notes and calculations, Ezio read:

... spring of horn or of steel fastened upon wood of willow encased in reed.

The impetus maintains the birds in their flying course during such time as the wings do not press the air, and they even rise upwards.

If a man weigh two hundred pounds and is at point n, and raises the wing with his block, which is one hundred and fifty pounds, with power amounting to three hundred pounds he would raise himself with two wings…

It was all Greek to Ezio, but at least he could read it – Agniolo must have transcribed it from Leonardo’s impenetrable scrawl. In that moment he saw Agniolo looking at him, and hastily turned his attention elsewhere. He knew how secretive Leonardo liked to be.

Presently Leonardo himself arrived from the direction of the old studio and bustled up to Ezio, embracing him warmly. ‘My dear Ezio! You’re back! I am so glad to see you. After all that’s happened, we thought…’ But he let the sentence hang there, and looked troubled.

Ezio tried to lighten his mood again. ‘Look at this place! Of course I can’t make head or tail of any of it, but I suppose you know what you’re doing! Have you given up painting?’

‘No,’ said Leonardo. ‘Just following up… on other things… that’ve caught my attention.’

‘So I see. And you’ve expanded. You must be prospering. The past two years have been good to you.’

But Leonardo could see both the underlying sadness and the severity that had settled in Ezio’s face now. ‘Perhaps,’ said Leonardo. ‘They leave me alone. I imagine they think I’ll be useful to whoever wins absolute control one day… Not that I imagine anyone ever will.’ He changed. ‘But what of you, my friend?’

Ezio looked at him. ‘There will be time, I hope, one day to sit down and talk over all that has happened since we last met. But now, I need your help again.’

Leonardo spread his hands. ‘Anything for you!’

‘I have something to show you which I think will interest you.’

‘Then you had better come to my studio – it is less busy there.’

Once back in Leonardo’s old quarters, Ezio produced the Codex page from his wallet and spread it on the table before them.

Leonardo’s eyes widened with excitement.