‘But how can this be? Who but God can know the future?’

‘Ah,’ said Thomas. ‘An interesting question.’

‘Which,’ Joan said hastily, ‘we can explore at our leisure another time. For now, Saladin, the important point is that this information has proved useful.’

Saladin nodded. ‘If you know the Mongols are coming you can arm against them.’

‘We tried that,’ Joan said. ‘But nobody wants to believe in the coming of the Mongols until they are on the doorstep.

‘What we could anticipate was the plight of the refugees - those poor folks driven ahead of the Mongols’ advance, in Asia, Persia, Europe. So we set up caravan stops. We supplied food and water, blankets. We even hired Saracen doctors. And we bought up the land to which they had to flee.’

‘We made money out of the terrified,’ Saladin said. He seemed faintly disgusted.

‘We saved lives,’ Joan said sternly. ‘There are far more ignoble ways of making a living, Saladin. And if we had not, our family could not have survived here.’

‘Think of it as a miracle,’ Thomas said to Saladin. ‘Everyone knows that the First Crusade’s dazzling successes all depended on miracles. Perhaps God has miraculously assisted your family, for purposes yet to be revealed. Think of it that way.’

‘But now,’ Joan said, ‘things have changed.’

‘How so?’

‘For one thing,’ Thomas said, ‘the Mongols have turned back. We must discuss the meaning of this in due course.’

Joan said, ‘And then there is this letter from Subh the Moor, our distant cousin. She drops a hint that the Codex, Sihtric’s engine designs, may not be lost after all . . .’ Subh had said that a copy of the lost plans might have been buried under the floor of the mosque in Seville. ‘If Robert ever knew this,’ Joan said, ‘he did not tell his son, or at any rate it was not written down.’

Now Saladin’s face was full of a boyish wonder, pleasing to Thomas’s dry heart. ‘Buried under a mosque! What a story!’

‘It may be just that,’ Thomas warned. ‘A story. But Subh has taken it seriously enough to write to you.’

Joan said, ‘Subh believes that all these fragments of prophecy, in her possession and ours, may be put back together into a whole, the prophetic lore reassembled for the first time since the age of Sihtric himself.’

‘And so that’s why she wrote to you?’ Saladin asked. ‘But what does she want? We are Christian, she is Muslim. The Christians are destroying her country. Perhaps she intends to trick us, as that old priest Sihtric intended to trick the Moors.’

Thomas said, ‘Even if that is her intention it need not be fulfilled. If we could get hold of these designs, if we could build the Engines of God, we could strike a devastating blow against Islam.’

Saladin studied him, curious. ‘That sounds a very military ambition for a monk.’