Someone had his left arm. He slammed his right fist and his pommel at this new threat – connected, and the man fell away – then he took a kick or a punch to his knee that caused him to fall backwards.

His head struck the stones that had almost tripped him as he entered the corridor. He hit hard – but his armet took the blow and his thickly padded liner saved him.

He could hear them coming, and he knew he was hurt, and more on impulse than by training he hauled himself over the rock – under his desperate hands, it became a stone column with deep fluting. He knelt because his left leg was having trouble supporting him, took his sword in both hands, and put the point up.

Forty feet down the tunnel, there was a scream and the last torch went out.

‘One, two, three! Charge!’ called a voice in Turkish. They had taken twenty of Swan’s gasping breaths to ready themselves.

Swan had used the time to get against the right-hand wall, crouched down behind the fallen pillar. He couldn’t see them. But he could certainly hear them.

They all screamed together – the long, undulating scream that had taken Constantinople.

The two leaders hit the pillar together. And fell.

Swan cut – in panic – at the sounds. Hit something soft, cut again, and again. And again. Cut – thrust, cut.

A desperate Turk, heroically brave, seized his sword-blade – probably in his death throes, but his sacrifice was not in vain. By luck, or fortuna, he plucked the blade right out of Swan’s hands. Swan felt it go – heard it fall.

A man hit his chest. And tried to wrap his arms about Swan’s shoulders.

Swan pulled the man over the column – every Turk had to discover the downed column for himself, and it had become Swan’s greatest advantage. He used it to break the man’s balance and threw him, and then fell atop him, steel-clad arms and hands working brutally.

A heavy weapon rang off his helmet. And there was suddenly weight on his back – he rolled, a man screamed, and Swan got his right hand on his rondel dagger. It was still there. He got it out – reversed – and stabbed with it.

He realized that the roaring sound was his own voice.

He felt the man’s neck go just as he pounded the blade into the man’s skull. The skull cracked like an egg and then the whole head collapsed under his weight. Then he felt himself repeat the blow, even though he knew the man had to be dead.

He tried to rise off the new corpse, but his leg failed him and he sank back – now kneeling on both knees. He could see nothing. He could hear at least two men dying. Everything smelled of blood, and faeces, and despair.

Perhaps he whimpered. He certainly wanted to.

That was how Fra Tommaso found him, when he came at the head of a dozen knights. Swan was still kneeling, facing the corridor. His armour was caked in blood and dirt, and he had a dagger blade in both hands, and he was weeping. He couldn’t stop it, and he couldn’t get his helmet open. As soon as he heard the Italian voices coming, he’d burst into tears.

He was ashamed of his weakness. But that only made him sob. He choked.

Fra Tommaso clutched him to his chest – steel to steel. Torches illuminated the charnel house – seven dead men, all looking as if they’d been savaged by demons or wolves.

‘Ave Maria!’ muttered Sir John Kendal.

Swan couldn’t speak. The man with the crushed skull had been Salim. He had time to see that before he vomited.

‘He’s bleeding,’ said Fra Tommaso.

It took them an hour to get him above ground, and in the end, he lost consciousness.

Swan dreamed about it and awoke, screaming. And Fra Tommaso comforted him.

Either this happened many times, or it was all part of the same nightmare. The dark. The choking heat, the faceplate, the smell of blood, the pressure of a man on his breastplate and the feel of the face caving in under his knife. Again, and again.

And again.

And again.

When Swan recovered himself, he had a moment of extreme disorientation as the man at the end of his narrow bed was Fra Domenico Angelo, known the length and breadth of the Inner Sea as Fra Diablo. The conqueror’s ring burned on his finger like the fire of God.

Swan tried to remember where he was. It probably said something about him that he knew the ring – and felt lust for it – before he came to the conclusion that he was in the Hospital of Rhodos.

He could taste the opium in his mouth. His left leg was wrapped like an Egyptian mummy’s.

The slightest flick of thought and he was in the dark with the weight of a man on his chest and—

‘The conquering hero,’ Fra Domenico said.

Down the ward, a man screamed.

Swan’s body spasmed. And he leaned over the bed and vomited into a basin.

Fra Domenico sat on his bed and kept his long hair out of his chamber pot. ‘Ahh,’ he said, in his disturbingly gentle voice. ‘It was bad, under the earth, wasn’t it, boy?’

Swan felt a disobedient temptation to punch the brother knight.

‘Listen, lad,’ the other man said. ‘That’s what it is like. And will be like, in your dreams, for many nights.’

Swan flashed on … darkness. Hot darkness. A skull bursting under his weight like a hot chestnut on the frozen Thames. He got hold of himself. ‘Sir …’ he panted. ‘What do I do?’

‘Pray,’ Fra Dominco suggested. He knelt, and began to pray – simple words; the Lord’s Prayer and the Ave Maria.

Two days passed. The bandages came off, and Fra Tommaso and Fra John came to take him to the English Langue. Peter came with clothes. Swan was so far from himself that he didn’t feel dirty and didn’t feel any need to shave. He simply put on the clothes.

Swan walked between them like a prisoner. He didn’t look around himself, and he didn’t have much of a sense of where he was. Sometimes he had trouble breathing.

Fra John Kendal brought him along the main street to the English tower, and together they climbed the internal stairs to the second floor, where the knight had his command post.

He sat. Swan sat opposite him with Fra Tommaso. Even Peter sat.

‘Talk,’ John Kendal said. ‘Tell it.’

Swan looked at the darkness for a long time. ‘Can’t,’ he said.

Peter leaned forward. ‘Sooner you tell it. Sooner it stops eating you.’

A cup of wine was put in front of him. He drank it without tasting it, and another, while the others talked.

Suddenly – without even intending to speak – he said, ‘It was hot and it stank and I liked Salim.’ He sobbed the last.

Peter sloshed wine into the cup. ‘Tell us.’

Swan swallowed wine. ‘I fought them. You know,’ he said. He made a motion.

The other two knights sat, silently. Tommaso leaned forward and put a hand on Swan’s shoulder. ‘We all know,’ he said. ‘Now you know, too.’

‘Who was Salim?’ Kendal asked.

Swan took a deep breath and steadied himself. ‘An African slave – a prisoner of war. He showed me the tunnels. Weeks ago. And he – I think he was the one – betrayed them to the Turks.’

Fra Tommaso splashed some of the wine into his own cup. ‘Hardly a betrayal,’ he said with a sad smile. ‘Hmm?’

‘He was the last man I killed,’ Swan said. And then it began to come tumbling out of him – phrase by phrase, like pus leaving a wound. The waiting. The fight.

And then the long nightmare in the dark, listening to them die.

Tommaso drank more. ‘Some of them got away,’ he said. ‘We saw them come out of the opening. Peter showed us. They had torches, and there was a sally. They threw a feint against the walls.’

Swan’s brain was beginning to function. ‘That makes sense,’ he said. ‘When some of them charged me – some ran.’

He drank more wine. ‘They couldn’t see me in the dark,’ he said. Almost as if he felt for them.

Peter frowned. ‘Polished armour is almost invisible in the dark,’ he said.

‘None of them had any armour,’ Swan added.