Without another word he turned and scaled the wall behind him at such a speed that Ezio was hard put to keep up. They raced over the red-tiled roofs, leaping the chasms of the streets in the last afterglow of the sun, silent as cats, soft-footed as running foxes, heading north-west across the city, until they arrived in sight of the façade of the great church of Santa Maria Novella. Here the Fox came to a halt. Ezio had caught him up in seconds, but he noticed that he was more breathless than the older man.

‘You’ve had a good teacher,’ said the Fox; but Ezio had the distinct impression that if he had so chosen, his new friend could have outrun him with ease; and that increased his determination to hone his skills further. But now wasn’t the time for contests or games.

‘That is where Messer Francesco is holding his meeting,’ said the Fox, pointing downwards.

‘In the church?’

‘Under it. Come on!’

At that hour, the piazza in front of the church was all but deserted. The Fox leapt down from the roof they were on, landing gracefully in a crouch, and Ezio followed suit. They skirted the square and the side of the church until they came to a postern-gate set into its wall. The Fox ushered Ezio through it and they found themselves in the Rucellai Chapel. Near the bronze tomb at its centre, the Fox paused. ‘There is a network of catacombs which crisscross the city far and wide. I find them very useful in my line of work, but unfortunately they are not exclusive to me. Not many know about them, however, or how to find their way about in them, but Francesco de’ Pazzi is one. It is down there that he is holding his meeting with the people from Rome. This is the closest entrance to where they will be, but you will have to make your own way to them. There’s a chapel, part of an abandoned crypt, fifty yards to your right once you have descended, and be very careful, for sound travels very acutely down there. It will be dark, too, so allow your vision to become accustomed to the gloom – soon you will be guided by the lights in the chapel.’

He placed his hand over a stone boss on the pedestal that supported the tomb, and pressed it. At his feet, an apparently solid flagstone swung down on invisible hinges to reveal a flight of stone steps. He stood aside. ‘Buona fortuna, Ezio.’

‘You are not coming?’

‘It is not necessary. And even with all my skills, two people make more noise than one. I will wait for you here. Va, go!’

Once below ground, Ezio groped his way along the damp stone corridor that ran away to his right. He was able to feel his way along, for the walls were close enough here for him to touch either side with each hand, and he was relieved that his feet made no sound on the wet earthen floor. Occasionally, other tunnels branched off and he could feel them rather than see them as his guiding hands touched nothing but a black void. Getting lost down here would be a nightmare, for one would never find one’s way out again. Little sounds startled him at first, until he realized that they were nothing but the scuttling of rats, though once, when one ran over his feet, he could barely stifle a cry. In niches carved into the walls, he caught glimpses of the corpses from timeworn burials, their skulls shrouded in cobwebs – there was something primordial and terrifying about the catacombs, and Ezio had to bite back a rising sense of panic.

At last he saw a dim light ahead, and, moving more slowly now, advanced towards it. He stayed in the shadows as he came within earshot of the five men he could see ahead, silhouetted in the lamplight of a cramped, and very ancient, chapel.

He recognized Francesco immediately – a small, wiry, intense creature who, as Ezio arrived, was bowed before two tonsured priests he did not recognize. The older of the two was giving the blessing in a clear, nasal voice: ‘Et benedictio Dei Omnipotentis, Patris et Filii et Spiritu Sancti descendat super vos et maneat semper...’ As his face caught the light, Ezio recognized him; he was Stefano da Bagnone, secretary to Francesco’s uncle Jacopo. Jacopo himself stood near him.

‘Thank you, padre,’ said Francesco when the blessing was concluded. He straightened himself and addressed a fourth man, who was standing beside the priests. ‘Bernardo, give us your report.’

‘Everything is in readiness. We have a full armoury of swords, staves, axes, bows and crossbows.’

‘A simple dagger would be best for the job,’ put in the younger of the two priests.

‘It depends on the circumstances, Antonio,’ said Francesco.

‘Or poison,’ continued the younger priest. ‘But it doesn’t matter, as long as he dies. I will not easily forgive him for bringing down Volterra, my birthplace and my only true home.’

‘Calm yourself,’ said the man called Bernardo. We all have motive enough. Now, thanks to Pope Sixtus, we also have the means.’

‘Indeed, Messer Baroncelli,’ replied Antonio. ‘But do we have his blessing?’

A voice came from the deep shadows beyond the lamplight at the rear of the chapel, ‘He gives his blessing to our operation, “provided that nobody is killed”.’

The owner of the voice emerged into the lamplight and Ezio drew in his breath as he recognized the cowled figure in crimson, though all of his face but the sneer on his lips was covered by the shadow of his hood. So this was the principal visitor from Rome: Rodrigo Borgia, il Spagnolo!

The conspirators all shared his knowing smile. They all knew where the Pope’s loyalty lay, and that it was the cardinal who stood before them who controlled him. But naturally, the Supreme Pontiff could not openly condone the spilling of blood.

‘It’s good that the job can be done at last,’ said Francesco. ‘We’ve had enough setbacks. As it is, killing them in the cathedral will draw heavy criticism on us.’

‘It is our last and only option,’ said Rodrigo, with authority. ‘And as we are doing God’s work in ridding Florence of such scum, the setting is appropriate. Besides, once we control the city, let the people murmur against us – if they dare!’

‘Still, they keep changing their plans,’ said Bernardo Baroncelli. ‘I’m even going to have to have someone call on his younger brother Giuliano to make sure he’s up in time for High Mass.’

All the men laughed at that, except Jacopo and the Spaniard, who had noticed his sober expression.

‘What is it, Jacopo?’ Rodrigo asked the older Pazzi. ‘Do you think they suspect something?’

Before Jacopo could speak, his nephew waded in impatiently. ‘It’s impossible! The Medici are too arrogant or too stupid even to notice!’