He snatched the papers that weren’t already burnt out of the fire and stamped the flames out. ‘Never give in to your temper,’ he advised them. ‘It can be terribly counter-productive.’

‘So what’s cured yours?’ asked Antonio.

‘Look!’ Leonardo said. ‘Did you not see the ashes rise? Heat lifts things up! How often have I seen eagles high in the air, not flapping their wings at all, and yet staying aloft! The principle is simple! All we have to do is apply it!’

He reached for a map of Venice and spread it out on the table. Leaning over it with a pencil, he marked out the distance between the Palazzo Pexaro and the Palazzo Ducale, putting crosses at key points between the two buildings. ‘Antonio!’ he cried. ‘Can you get your people to build bonfires at each of the places I’ve marked, and light them in a close sequence?’

Antonio studied the map. ‘I think we could arrange that – but why?’

‘Do you not see? This is Ezio’s flight path! The fires will carry my flying machine and him all the way to his target! Heat rises!’

‘What about the guards?’said Ezio.

Antonio looked at him. ‘You’ll be flying that thing. For once, leave the guards to us. In any case,’ he added, ‘some of them at least will be busy elsewhere. My spies tell me there’s a curious shipment of coloured powder in little tubes which has just arrived from a country far away to the east called China. God knows what it is but it must be valuable, they’re taking such good care of it.’

‘Fireworks,’ said Leonardo to himself.

‘What?’

‘Nothing!’

Antonio’s men had the fires Leonardo had ordered built and ready by dusk. They had also cleared the areas around them of any watchmen or idle bystanders who might be inclined to warn the authorities of what was afoot. Leonardo’s assistants had meanwhile transported the flying-machine to the Pexaro roof once more, and Ezio, armed with his spring-blade and arm-guard, had taken up his position in it. Antonio stood nearby.

‘Rather you than me,’ he said.

‘It’s the only way to get into the palace. You said so yourself.’

‘I never dreamed this could actually happen, though. I still find it almost impossible to believe. If God had meant us to fly -‘

‘Are you ready to give the signal to your men, Antonio?’ asked Leonardo.

‘Absolutely.’

‘Then do so now, and we’ll get Ezio airborne.’

Antonio walked to the edge of the roof and looked down. Then he took out a large red handkerchief and waved it. Far below they could see first one, then two, three, four and five huge bonfires leap into flame.

‘Excellent, Antonio. My congratulations.’ Leonardo turned to Ezio. ‘Now, remember what I told you. You must fly from fire to fire. The heat of each one as you pass over it should keep you in the air all the way to the Ducal Palace.’

‘And be careful,’ said Antonio. ‘There are archers posted on the roofs and they’ll certainly shoot as soon as they see you. They’ll think you’re some demon from hell.’

‘I wish there was some way I could use my sword at the same time as flying this thing.’

‘Your feet are free,’ said Leonardo thoughtfully. ‘If you manage to steer close enough to the archers and avoid their arrows, you might be able to kick them off the rooftops.’

‘I’ll bear that in mind.’

‘And now you must go. Good luck!’

Ezio sailed off the roof into the night sky, setting a course for the first fire. He was beginning to lose height as he approached, but then, as he reached it, he felt the machine lift again. Leonardo’s theory worked! On he flew, and he could see the thieves tending the bonfires look up and cheer. But the thieves were not the only ones aware of him. Ezio could see Barbarigo archers posted on the cathedral roof and on the other buildings near the Doge’s Palace. He managed to manoeuvre the flying-machine out of the way of most of the arrows, though one or two thudded into its wooden frame, and he also managed to swoop low enough to knock a handful of bowmen off their perches. But as he approached the Palace itself, the Doge’s own guards opened fire and they were using fire-arrows. One caught in the starboard wing of the machine and it immediately burst into flames. It was all Ezio could do to keep on course, and he was losing height fast. He saw a pretty young noblewoman looking up and screaming something about the devil having come to claim her, but then he was past. He let go of the controls and fumbled with the harness buckles which held him in. At the last moment he wrenched himself free and leapt forwards and outwards, to land in a perfect crouch on an inner courtyard roof, past the grille which guarded the palace interior from all but the birds. Looking up, he saw the flying-machine crash into the campanile of St Mark’s and its wreckage fall to the square below, causing panic and pandemonium among the people there. Even the ducal archers’ attention was diverted, and Ezio took advantage of that to climb swiftly down and out of sight. As he did so, he saw Doge Mocenigo appear at a second-storey window.

‘Ma che cazzo?’ said the Doge. ‘What was that?’

Carlo Grimaldi appeared at his elbow. ‘Probably just some youths with firecrackers. Come, finish your wine.’

Hearing that, Ezio made his way via roofs and walls and, taking care to keep out of sight of the archers, to a spot just outside the open window. Looking in, he saw the Doge draining a goblet. He threw himself over the sill and into the room, exclaiming, ‘Stop, Altezza! Don’t drink – !’

The Doge looked at him in astonishment as Ezio realized he had arrived a moment too late. Grimaldi smiled wanly. ‘Not quite your usual accursed good timing, young Assassin! Messer Mocenigo will be leaving us shortly. He’s drunk enough poison to fell a bull.’

Mocenigo rounded on him. ‘What? What have you done?’

Grimaldi made a gesture of regret. ‘You should have listened to me.’

The Doge staggered and would have fallen if Ezio had not rushed forward to support him and guide him to a chair, where he sat down heavily.

‘Feel tired…’ said the Doge. ‘... Going dark…’

‘I am so sorry, Altezza,’ said Ezio helplessly.

‘About time you tasted failure,’ snarled Grimaldi at Ezio, before flinging open the door of the room and bellowing, ‘Guards! Guards! The Doge has been poisoned! I have the killer here!’

Ezio sprang across the room and grabbed Grimaldi by the collar, dragging him back into the room, banging the door shut and locking it. Seconds later he heard the guards running up and hammering on it. He turned to Grimaldi. ‘Failure, eh? Then I’d better do something to make up for it.’ He released his spring-blade.