‘During which, you were fed and did no work at all by my command,’ Swan said.

The two men looked at each other for a moment.

‘You have been a slave?’ the black asked carefully.

‘Only for a little while,’ Swan said.

‘Clearly the effendi learned some essential matters,’ the African said. ‘I am called Salim, here. Out there,’ he said, waving, ‘I am Mohamed.’

Swan nodded. ‘Call me Tommaso,’ he said. ‘Now show me where they were found.’

‘I can do better, if you pay me,’ the African said. ‘I can show you what the two fools didn’t know – how to reach the ancient city under the sewers.’

‘Are you a prisoner of war?’ Swan asked.

Salim nodded.

Together, they climbed an old house – really a tower, and probably more than a thousand years old. The inside was occupied by beggars who lived in the basement, and all the floors had fallen in and been salvaged for furniture, for room dividers, and even as firewood.

‘Can’t we go in by the door?’ Swan asked while climbing the sun-heated stone of the outer wall.

‘No,’ said the slave. He offered no further information.

Swan wondered whether he was being precipitate in trusting the man, and touched the needle-sharp rondel dagger at his waist. Just in case. They got over the old roof trees and then descended on ropes obviously there for the purpose.

There were other people living in the ruin, and the whole of the old tower was a chimney, so that they climbed down through a variety of cooking smells – onions, some meat, cardamom – all delicious.

Salim seemed to know the occupants, and he and Swan passed among them with only some murmurs. They went down into the old tower’s basement, and then along a short stone-lined corridor that stank of urine, and into an obvious cesspit.

‘Jesus!’ Swan spat.

Salim made a face. ‘Must you swear, Christian?’ he asked.

Swan would have laughed, but the stench made him retch.

The slave raised the hem of his kaftan and Swan pulled his gown tight against his body, and the two men edged along the least polluted wall and into another stinking corridor on the far side.

‘Did I fail to mention that the entry route is used as a set of privies?’ Salim asked with a wicked smile.

Swan grunted. ‘Did I fail to mention that I have a dagger and you do not?’ he asked idly, in Arabic. ‘Even a scratch would be septic, in this.’

‘Uhhnn.’ Salim nodded, not displeased.

While Swan contemplated the Arabic sense of humour, they passed six cesspits, each more odiferous and disgusting than the last, until they emerged into a dark chamber that stank only of cat piss. Swan lit an oil lamp, which guttered, as if the fumes ate the air. But the slave knew where there were lanterns and torches hidden in the rocks, and they made their way along an odd path – almost like a street, except that Swan could tell he was looking at shorings and foundations – heavy stone with an outward slope.

He stepped on something that bit at his foot. Examination under torchlight revealed a bronze arrowhead – light, and with a trilobite head. Swan had seen them before – at Marathon.

‘Persian!’ he said.

The black man shrugged. ‘If you say, Effendi. You are not expecting treasure, I hope.’

Swan smiled. ‘If there was a treasure …’ he said.

Salim raised a black eyebrow. ‘Yes?’ he asked, pausing. The torchlight rendered his face demonic.

‘You wouldn’t take me here at all,’ Swan said.

Salim laughed. ‘Sometimes there are coins. Arrowheads, such as the one you found. It was a great battle, the one the ancient men fought here before the Prophet, may his name be blessed, came to teach men the way of justice.’

‘How much farther does this go?’ Swan asked.

‘All the way to the—’ Salim seemed to catch himself. ‘Not much farther. Sometimes we find different tunnels—old streets. The old slaves say there is a tunnel cut in the rock—all the way under the walls to the south.’ He shrugged. ‘I have never seen it,’ he said.

Swan was increasingly conscious of being under the earth with a man as big as he was and every bit as dangerous. At the same time, he recognized the stone in the torchlight as marble—heavily veined grey marble. From ancient Greece.

‘It is fascinating,’ Swan said. ‘But I have to be at dinner in the hall. Shall we go back?’

‘Yes,’ Salim said, with some relief. He led the way, apparently unconscious of Swan’s careful movements behind him.

Spring came early in Greece. The flowers burst forth, so that the fields outside the town were like intricate Persian carpets, with tiny flowers each a different colour as far as the eye could see.

The first ship in from Italy brought news of a great peace. There was immense excitement in Rome, and Nicholas V, the Pope, was convening a great council to declare a crusade to rescue Constantinople.

Swan heard all this over a cup of wine. He walked quickly back to his barracks and found Fra Tommaso – only to have his bubble of militant Christian enthusiasm burst by the old man’s cynicism.

‘Peace between Sforza and Venice – certainly. I’d heard of it before we cleared Ancona,’ Fra Tommaso said. ‘Peace in Italy? I suppose it’s possible.’ He laughed. ‘A crusade? Honestly, young man, where do you get these notions? No one in Europe actually cares about the loss of Constantinople! The Italians want to make money, the French want to make war, the English … perhaps want to make beer. The Emperor, may his name be praised, is busy trying to make certain there won’t be a crusade, and trust me, that will be his view right up until Mehmet marches to the gates of Vienna.’

Swan sagged. ‘Oh.’

‘Listen, boy, you’ve been listening to all the Burgundians and the Frenchmen. They’re eager for a crusade. Good for them – it’s not their cargoes that the Turks will seize. But without a fleet – a fleet of both Venice and Genoa – there is no crusade. Eh?’

‘So now what happens?’ Swan asked. ‘We’re ready for sea.’ He thought of the awesome labyrinth under his feet, barely explored.

‘As to that – what happens now is that you and I take our ship down to Alexandria, to pay our loving respects to the Mamelukes, who are every bit as much Muslims as the Turks but are preferred by his Holiness. Understand?’ He laughed again.

‘No,’ Swan said.

‘Good. We’ll sail in the morning. Get your kit aboard.’ Fra Tommaso waved his hand.

Alexandria was everything that Swan thought a city should be. It was huge – unbelievably big, really, with so many different markets and bazaars that the Englishman wandered from morning until night while the order’s delegation met the Sultan and paid their respects – and some kind of secret tribute.

After a day as a Christian tourist, Swan decided to see the city as a co-religionist. He had the clothes – all his Turkish clothes had been with Peter, and he liked the idea of going as a Turk, which would prompt fewer questions about any accent there might be to his Arabic. He went ashore in his military gown and changed in the public privy behind the beachfront bazaar. He rolled his Christian clothes into a tight bundle and placed them in the bottom of the small leather bag he carried. Dressed as a Christian, every move he made would be reported.

Especially a visit to a brothel.

Dressed as a Turk, he wandered through the waterfront souk, waiting to be challenged. But no such thing took place. Instead, he received a great deal of fawning, and he developed a following of a crowd of small boys, whom he pleased by buying them sweets.

A woman took the sweets away from one boy and threw them in a pile of dung.

‘You know what the Turk wants you for,’ she spat in Arabic that he wasn’t supposed to understand.

The boys all fled.

Swan shook his head and continued through the string of markets.

Alexandria was a dream city – a city almost two thousand years old, and built for trade. The magnificent harbour was packed with Genoese and Venetian shipping, as well as a scattering of French ships and – of all things – an English ship, the Katherine Sturmy. He almost forgot his position as a Turk when he heard a man speak in English – and heard a woman answer him.