They continued further up the slope, coming to the upland just as the gates to the fortress finally opened. More Assassins poured through them, yelling and ready for the fight.

Behind him he heard the villagers scream and scatter, although Mukhlis was urging them to stay. Altaïr turned to see him throw up his hands, but he couldn’t blame the people for their loss of resolve. They all knew of the fearsome savagery of the Assassin. No doubt they had never seen two opposing Assassin armies fight and neither did they want to. What they saw were marauding Assassins come howling from the gates with bared teeth and flashing swords, their boots drumming on the turf. They saw Altaïr’s supporters crouch and tense, readying themselves for action. And they took shelter, some running for cover behind the watchtower, others retreating down the hill. There was a great shout and a crash of steel as the two sides met. Altaïr had Malik as his bodyguard, and he kept an eye on the ramparts as the battle raged – the ramparts where the archers stood, perhaps ten of them. If they opened fire the battle was surely lost.

Now he saw Abbas.

And Abbas saw him.

For a moment the two commanders regarded one another, Abbas on the ramparts, Altaïr down below – strong and still as rock as the battle whirled around him – the best of childhood friends turned the bitterest of enemies. Then the moment was broken as Abbas yelled at the archers to fire. Altaïr saw uncertainty on their faces as they raised their bows.

‘No one must die,’ called Altaïr, entreating his own men, knowing that the way to win over the archers was by example. Abbas was prepared to sacrifice Assassins; Altaïr was not, and he could only hope that the hearts of the archers were true. He prayed that his supporters would show restraint, that they would give the archers no reason to open fire. He saw one of his men fall, howling, his throat open, and straight away the loyalist Assassin responsible was attacking another.

‘Him,’ he instructed Malik, pointing in the direction of the battle. ‘Take him, Malik, but be merciful I urge you.’

Malik joined the battle and the loyalist was pushed back, Malik swiping at his legs. When his opponent fell, he straddled him and delivered not a killing blow but a strike from the hilt of his sword that knocked him senseless.

Altaïr looked up to the ramparts again. He saw two of the archers lower their bows, shaking their heads. He saw Abbas produce a dagger – his father’s dagger – and threaten the men with it, but again they shook their heads, lowering their bows and placing their hands to the hilts of their swords. Abbas wheeled, screaming at the archers along the rampart behind him, ordering them to cut down the defectors. But they, too, were lowering their bows and Altaïr’s heart leaped. Now he was urging his men forward, to the gates. Still the battle continued but the loyalists were slowly becoming aware of events on the ramparts. Even as they fought they exchanged uncertain glances, and one by one they stepped back from combat, dropping their swords, arms held out, surrendering. The way was clear for Altaïr’s party to advance on the castle.

He led his men to the gates and rapped on the door with his fist. Behind him assembled the Assassins – and the villagers were returning, too, so the upland was thronged with people. From the other side of the castle gate there was a strange stillness. A hush descended over Altaïr’s people, the air crackling with expectation, until suddenly bolts were thrown and the great castle gates swung wide, opened by guards who dropped their swords and bent their heads in deference to Altaïr.

He nodded in return, stepped over the threshold, under the arch, and walked across the courtyard to the Master’s tower. Behind him came his people; they spread out and flowed around the edges of the courtyard; archers descended the ladders from the ramparts to join them, and the faces of families and servants were pressed to the windows of the towers overlooking the grounds. All wanted to witness Altaïr’s return, to see his confrontation with Abbas.

He climbed the steps to the platform, then moved into the entrance hall. Ahead of him, Abbas stood on the steps, his face dark and drawn, desperation and defeat all over him, like a fever.

‘It is over, Abbas,’ called Altaïr. ‘Order those who are still loyal to you to surrender.’

Abbas scoffed, ‘Never.’ At that moment the tower opened and the last of the loyalists came from the side rooms into the hall: a dozen or so Assassins and manservants. Some had skittering, frightened eyes. Others were fierce and determined. The battle was not over yet.

‘Tell your men to stand down,’ commanded Altaïr. He half turned to indicate the courtyard, where the crowds were gathered. ‘You cannot possibly prevail.’

‘I am defending the citadel, Altaïr,’ said Abbas, ‘to the last man. Would you not do the same?’

‘I would have defended the Order, Abbas,’ snarled Altaïr. ‘Instead you have sacrificed everything we stand for. You sacrificed my wife and son on the altar of your own spite – your blank refusal to accept the truth.’

‘You mean my father? The lies you told about him.’

‘Isn’t that why we’re standing here? Isn’t that the wellspring of your hatred that has flowed through the years, poisoning us all?’

Abbas was trembling. His knuckles were white on the balustrade of the balcony. ‘My father left the Order,’ he said. ‘He would never have killed himself.’

‘He killed himself, Abbas. He killed himself with the dagger that you have concealed within your robe. He killed himself because he had more honour than you will ever know, and because he wouldn’t be pitied. He wouldn’t be pitied as you will be, by all, as you rot in the citadel dungeon.’

‘Never!’ roared Abbas. He pointed a trembling finger at Altaïr. ‘You claim you can retake the Order without loss of Assassin life. Let’s see you try. Kill him.’

And suddenly the men in the hall were surging forward, when …

The sound of the explosion echoed around the hall and silenced everyone – the crowds in the courtyard, the Assassins, the loyalists. All stared in shock at Altaïr, who stood with his arm held up as if pointing at Abbas – as though he had been engaging his blade in the direction of the steps. But instead of a blade at his wrist there was a curl of smoke.

From the steps came a short, strangled cry, and all watched as Abbas stared down at his chest, where a small patch of blood on his robe was gradually spreading. His eyes were wide with shock. His jaw worked as he tried to form words that wouldn’t come.