Alessandro nodded. ‘This is an excellent plan,’ he said. ‘Let me give you a word of advice.’

Swan nodded.

‘Do not – I beg leave to repeat myself – do not seek to avenge yourself on Omar Reis.’ Alessandro rose and poured more wine. ‘We have our date. The Sultan will receive the papal ambassador in three days’ time. We are to leave the city immediately after.’ Alessandro handed him wine. ‘Whatever you do, you must be back in three days. And no revenge. Understood?’

Swan nodded. ‘Of course not. That would be stupid.’

An hour later, he had exchanged notes with Simon. Several hours later, a Greek wine merchant came into the Venetian quarter, and sold Candian wine to the Venetians by the hogshead from two wagons. A servant jumped down from the rear wagon and found Alessandro, and gave him a package.

Alessandro handed it over to Swan. It contained a set of directions and a full set of clothes – ragged, Greek clothes. Swan shook his head. ‘When do I get to dress well?’ he asked, and became a ragged Greek veteran, a penniless beggar. Peter became another such.

Alessandro shook his head. ‘Your whole plan depends on this Jew.’

‘Yes and no,’ Swan said. ‘I have something for him, as well.’ Then he and Peter went into the shadow of the gate.

Together, they waited their moment, and while the Greek wine merchant’s wagons stopped by the janissary, they slipped out.

The two of them moved carefully. Peter was too tall to avoid notice, but Swan needed him.

He almost laughed aloud when a pair of Greeks stopped and gave them alms.

‘At least you fought,’ said the elder. He clasped Peter’s hand.

‘He’s lost his voice,’ Swan said. ‘We fought, and we’ll keep fighting.’

The two men looked both pleased – and guilty. They handed over more coins and walked away quickly.

Peter shook his head. ‘They’re afraid,’ he said, in French.

Swan followed the route as laid down by Simon. He assumed that Simon was having them watched, checking to see that they were alone. He hoped so.

After walking over half the city, they came down Third Hill on a steep street. As they descended, a heavy grain wagon pulled across the narrow street. A pair of men jumped down.

They had crossbows.

‘Get on,’ said the one who looked as if someone had burned his face off.

The second man stood well clear of them. A small boy in the back of the wagon lifted the edge of a tarpaulin and they slipped in under the load of hay. It was stifling hot, and Swan immediately had to sneeze.

‘I don’t like this,’ said Peter.

The wagon rattled and clanked over the streets. It had no suspension, and Swan’s head cracked against the bottom several times before he found a better way to lie. He sneezed and sneezed, and one of the guards ordered him to be quiet.

Peter put a linen coif – none too clean – over his mouth. ‘We’re passing a guard post,’ he hissed.

Swan managed to keep his sneezes to himself for a hundred long heartbeats, and then the wagon was moving again.

Moments later, the top was stripped back, and Simon was standing with six armed men.

‘What have you done?’ he asked. But he seemed more amused than anything. ‘You promised me a secret and a profit in your note,’ he said.

Swan sneezed.

Later, dressed in an ornate robe and curly slippers, Swan leaned back on comfortable cushions.

‘So you are an agent of the cardinal,’ Simon said.

‘Perhaps,’ Swan said. ‘My only orders are to retrieve his library. Can you help me?’

Simon rocked his head from side to side. ‘Perhaps. It is risky. Everything is watched right now. You know that a great many of the Christian relics have gone missing – from Hagia Sophia, from the monasteries, from private houses. The Sultan is furious.’

‘None of my concern. I’m here for books. When I’m done, you may have the house,’ Swan said.

Simon made a face. ‘Is it yours to give?’

‘Of course,’ Swan said. ‘I’ll have your brother send you a deed.’ He shrugged. ‘A palace near the Hippodrome for some information and a little smuggling . . .’

Simon lay back and drank quaveh.

‘Let me understand this,’ he said. ‘I get you to the house from the Venetian quarter. You go inside and prepare the items you want to ship. I ship them to Galata for you, and I keep the cardinal’s house.’

Swan nodded.

It was an excellent plan, and the only hitch he could see was that Simon planned to sell him out. He could see it on the man’s face. Damn it.

Why are people so greedy?

‘How long will you be?’ Simon asked.

‘At least a week,’ Swan answered, an utter lie. In his head, he’d already discarded Simon.

‘That long?’ Simon said. ‘Why?’

‘It will take me that long to figure out what to take and what to leave,’ Swan said, embroidering as he went. ‘I’ll contact you when we’re ready. You get us from the Venetian quarter to the cardinal’s house. I’ll take care of the rest.’ In fact, in his head, he was already moving on to his next plan, but he needed to part amicably from this man before he chose to betray Swan immediately.

He and Peter said their goodbyes, and slipped out of the Jewish quarter at the guard change. They were followed.

‘He’s going to sell us,’ Swan said.

Peter sighed. ‘I wondered.’

‘We have to disappear. Luckily, we can.’ Swan took a deep breath. ‘Let’s buy food.’

They walked back towards the Venetian quarter. Swan’s fear at every corner was that the two men following them – Simon’s men – would sell them to the Turks on the spot, but they made it to the market, and purchased meat pies. And then they cut across the ruins of the old Forum – down the steep sides of the collapsed fountain, and into the sewers. No one following them had had a sightline. Or so Swan had to hope.

An hour later, they were in the underground cisterns, eating meat pies made of the same parts of the cow and the pig that were used in meat pies in London. There was more pepper, but the taste was strangely familiar.

Peter looked at the apparently endless arches receding into the distance. ‘This was built – by men?’

Swan slapped him on the back. ‘I’m glad you like it. We’ll be down here for a long time.’

As it proved, it took them two days and a night to find Bessarion’s house and explore the system. They were involved in necessary adventures, including the theft of a ladder from a monastery and carrying it underground and above ground for almost a mile; another theft of rope, and a tedious amount of sneaking through alleys, dropping coloured cloth through the gratings and then hurrying below to see where, exactly, they were.

Once, Swan had to hope his Greek was sufficient, and went above to purchase supplies. He walked carefully, watched carefully, and dealt with the deafest old woman he could find in the main market by the Hippodrome.

When they were sure – reasonably sure – that they had the right well, Swan lay on the walkway, on a stolen blanket, and drew a map of every part of the sewers and cisterns as he knew them. As far as he could see, the canals were underground cisterns carrying water from the aqueducts to supply the Hippodrome and the palace quarter and any houses lucky enough to be along the major water routes. Great houses simply had a well cover that opened into a shaft that ran down into the cistern. Some houses had private cisterns – and there was more than one cistern system, and they didn’t all link up. Or rather, in the time he had, Swan couldn’t see where they linked, and he and Peter often had to cross an alley or a small hill above ground, carrying all their tools, stumbling, lost in a darkened city.

The main canals, or cisterns, had iron rings every so often, and nautical bollards at intersections, clearly for tying small boats against the current. Swan couldn’t discern whether there were still maintenance crews working. As far as he could see, the newest stonework was two hundred years old or older, and there were four major cave-ins unrepaired.