A shadow crossed the room; a candle flickered. The vizier stood in the doorway, an armed guard at his side. 'And all that matters to me, priest, is that at last I have proof of your treachery.'

Alone in the dark, Robert measured space and time.

The floor was square, thirty by thirty of his foot-lengths paced out toe against heel. He could not see the ceiling, but he knew that many of the palace's rooms were rough cubes, so he imagined the room was as tall as it was wide. He explored the walls with his fingers. The room had arched doorways, but they were bricked up, save one closed by the heavy wooden door that had slammed shut after he had been thrown in here by the vizier's guards.

And he measured time. There was no passage of day or night; the bright Spanish sunlight was banished from his life. But he counted the meals that were shoved through a hatch in the door – bread, rice, a bit of water, delivered with a precious splinter of light. He counted his own pissing, his stools. He counted the times he slept, but his sleeping was poor.

In the dark he became confused in his counting, which distressed him.

It took him some of that passing time to work out that he was, in fact, imprisoned. There were few gaols in England, no cells save for a few dismal dungeons beneath the Normans' keeps, where athelings or other valuable captives might be held. If you committed a crime you might be executed, or mutilated, or fined; if you lived you went back to work. There wasn't the spare food to feed a population of prisoners. In al-Andalus, it seemed, things were different.

And as the days wore away and it dawned on Robert that he could see no end to this captivity, a deep horror settled on him.

He prayed every day, of course. Prayed every hour. Prayed constantly. He tried to mark Sunday, when he thought that day came. He recited the words of the holy Mass, as best he remembered them. Praying was better than thinking. Better than wondering what had become of his father, or Moraima, better than endlessly speculating why he had been thrown into this hole. Better than wondering what might become of him when he was finally released. Or, worse, how it would be if he were never released at all.

After the first few days he decided that he should treat his captivity as a trial. He thought of heroic monks like Saint Cuthbert, who deliberately sought out purposeful solitude in order better to understand their own souls, and God. If he were to become a soldier of God, fighting in the Pope's armies, he would face far worse torments than this.

He longed to be with Moraima. And he longed for his father to come and save him. But these were the weak thoughts of a child and he put them aside. He would use these hours in the hot, foetid, alien dark to cleanse his soul of weakness.

By the time his captors came for him, he thought only of God.

The door opened, flooding the cell with light. Two burly guards dragged him out of the dark. He was dazzled by the brilliance of a low sun. But he thought the guards flinched from the new holy light that burned from his own eyes.

Robert was shoved inside a reception room. Released, he staggered, and stood upright.

He glanced around. Books, bound volumes and scrolls, were piled roughly in one corner. Four arched doorways were all blocked by the burly bodies of guards – dark, stocky, powerful men, Berbers perhaps. The room was beautiful. But he had no time for beauty now; this was just as much a prison as his own shit-filled cell.

But Moraima, sweet Moraima was here too.

Moraima came to him, her hands folded into an anxious knot. A delicate scent of jasmine hung around her. He longed to take her in his arms, to let out the warmth that surged inside him. But he knew he must not.

She stood before him, uncertain how to read him. 'Robert. It has been so long. I thought they might have killed you. The vizier is like the weather; he comes and goes in his moods. He got angry with Sihtric, and he just locked everybody away.' She said hastily, 'I don't know what's happening here, Robert. But we must talk.' And she placed a hand on her belly.

Now Orm and Sihtric were brought in. Robert saw that they, too, had been imprisoned. Orm's beard was ragged, his hair untrimmed, the dirt ground deep into his pores, and there was a sewer stink of the cell about him. The priest, too, was shabby, and he scratched himself under a grimy habit.

Orm ran to his son and took his shoulders. 'Robert. What did they do?'

'I was stuck in a hole. They kept me in the dark.'

'In the dark, and alone? And we thought we had it bad, priest.'

'I am not harmed.'

Orm looked deep into his eyes, troubled. 'Are you sure? You look different.'

'Harder, I'd say,' said Sihtric. 'Not necessarily a bad thing, a bit of toughening up.'

'Shut up,' Orm said. 'Come sit over here.' They settled on floor cushions. 'Robert, I'm sorry.'

'Why?'

'Because it's my fault.'

Robert felt impatient that his father and this flawed priest were drawing the crisis about themselves like a cloak. 'How is it your fault? You were imprisoned too.'

Orm scratched his stubble. 'But I fear all this came about because of my foolishness – ours.'

He told Robert about the conversation he had had with Sihtric in another corner of the palace, about the Engines of God, and the Testament of al-Hafredi, and Sihtric's real intentions.

'Evidently we were overheard,' Orm said.

Sihtric said glumly, 'I've used that room for years.'

'But that part of the palace,' Orm told Robert, 'was an ambassador's court. It is a warren of tunnels and spy-holes. Moraima knew all about it. And this priest never thought to inquire.'

Sihtric snapped, 'But the vizier learned nothing damaging before you showed up in al-Andalus, Orm, with your addled prophecy, your doves and serpents, your doubts. Nobody before you ever encouraged me to express dreams I had kept safely lodged in the silence of my soul all these decades. You upset everything, Orm, all my delicate arrangements. Now he knows it all…'

Robert looked at the two squabbling old men. They didn't matter to him now. Their babbling of history and prophecy was irrelevant – and so, he thought for the first time in his life, was his father. All that mattered to Robert was the cold steel of the piety he had discovered in himself during his solitude.

'What a touching scene.' The vizier walked into the room.

They all got to their feet.

Ibn Tufayl looked magnificent in his djellaba of the finest silk and spun wool and with his skin shining with oils, yet he swayed, subtly. 'Three shabby Christians. How low you are. How animal-like. And the stink of you.'

'If you're going to kill us,' grated Orm, 'get it over with.'

'Oh, I fully intend to do that. But there's no rush, Viking. After all this time we still have much to say to each other. Sit down, all of you.'

He crossed the chamber, alone save for a single servant who bore a tray of sweetmeats and drinks. He walked stiffly, his posture erect. But Robert saw the cautious pacing of a man concentrating on control.

'The man is as drunk as a Breton,' Orm murmured.

'Then God help us all,' whispered Sihtric.