She had been there for nearly four months when he appeared. She was working fifteen-hour shifts. Sleep had become a dreamless refuge.

She emerged from one of these nightly comas into an orange morning. The camp was quiet at 6am. There were no twelve-year-olds who would soon be footless, no pickup trucks of bleeding villagers. These began to arrive after 7am, the casualties of dawn assaults.

She ate her customary breakfast quickly – coffee and a small bowl of porridge. The diet had become oppressive. Every day lunch was the same: sorghum flatbreads and goat stew. The organisation made a gesture to Western cuisine in the form of chicken legs, flown in on the UN plane every month and pushed to the bottom of the vault-like meat freezer. She had eaten no fish. She found that a dull desire, not as sharp as a craving, had taken hold of her bones. There was an oily base to the hunger.

She walked to the triage tent. Out of the corner of her eye she caught sight of a man leaning against the wall. She couldn’t remember seeing him before, couldn’t remember pulling him out of the flatbed of a pickup truck.

He approached her. He was like a greyhound, quick, aquiline. There was a flash in his eye, a firmness to the slant of his mouth. His age was hard to judge, but then it was, generally, here. The twenty-eight-year-old doctors and logistics managers who worked with her looked twelve. The thirty-two-year-old Bora and Nisa she soldered back together looked sixty-three.

He reached her. ‘I would like to show you something.’

His English hit her like a blow. She had yet to meet an insurgent who would admit to having learned a word of the infidel’s language, although many did speak it more than adequately, a result of their training in Yemen. Anthony had shown her surveillance drone photographs of a neat, fold-away camp in the mountains two hundred kilometres from Sana’a, in a hill fort that had been the British cavalry headquarters at the turn of the century.

He took out a notebook. It had black covers and ruled pages and was bound by a black elastic. Bound tight to the notebook was a pen. ‘I will have to translate.’ He leafed through it. He gave her a hesitant look.

She studied him. His lean frame suggested he was a Bora, although he was not particularly tall. He was most likely from the coastal city of Gao. Most of the men who evaded their questions were from there. She had never been to the city but she had read books and seen photo essays on the once grand resort city. The photographs she had seen were from the 1930s and showed wide, tiled avenues fringed by thin palms. It looked like Rio de Janeiro. There was even an art deco cinema in town, sandwiched between two Italian restaurants: the names were visible in the bleached black-and-white images: the Terraza Roma, the Toscana.

The city was sandwiched between the desert and the same ocean she would come to know in the Dhow House. But the city had lost any sense of its original geography. Entire blocks had vanished in the civil war. Gutted hotels surveyed the Indian Ocean like open-mouthed old men. Former foreign consulates stood roofless to the scald of sun. Gao’s salmon-coloured buildings had once been garlanded with second-storey balconies fringed by filigreed stonework. Its mosques had been as white as those she would later see in Kilindoni, their minarets traced in green trim. The beachfront had the same ivory sands, shallow warm waters patrolled by black-tipped reef sharks, the desert rose growing on its edge.

The man proceeded to read from his notebook. It was a story he had written, he informed her. The story was about a man who died from shark bite – one of the many sharks that scissored the cold waters off the coast of Gao, only to be reincarnated as a pair of spectacles. Everyone put him on their faces, the man told her, and their sight was instantly corrected. Widows saw the reasons for their husbands’ deaths and thanked God for having given them the opportunity to die as martyrs. Children saw their true vocation as soldiers of God. They stopped longing for the streets of the old capital with its bars and Italian magazines, its DVD stalls and mandolin players.

‘And the sharks?’ she asked.

‘The sharks are too big to wear the spectacles, so they go on killing senselessly.’

She listened in his voice for any note of irony. Finally she said, ‘So it’s a parable. You are the man who becomes a pair of glasses.’

He gave her a solemn, nearly nostalgic look. He was not strident. He didn’t seem to have the self-destructive stubbornness others of his kind displayed. His manner was mild but watchful.

The sun’s tangerine flare caught his face and turned his skin to bronze. He pointed towards the dressing swaddling his left abdomen. He must have been operated on two or three days before.

‘How long will I take to heal?’

‘I’ll do an examination tomorrow and tell you then.’

‘I must go home. My father is waiting for me.’ He named a village not far from Gao. His face lightened at the sound of its name, but his eyes remained two pieces of coal. ‘You won’t tell them?’

‘Tell who?’

‘Who you speak to, over there,’ he flung his right hand north, an errant compass.

‘We are doctors.’

She saw his eyes search her face and fail to find what they were looking for.

He gave his name as Ali. She struggled to picture his body on the operating table. She must have operated on five different men the morning Ali arrived. With his clipped, martinet stride she would recognise his walk in a crowd of similar thin, impala-haunched men. His skin was darker than most, he was not particularly tall or imposing, but he had a commanding quality. He was very thin, a result of his wounds, lack of food, years of loping through the desert and the natural physique of his tribe, the Bora. ‘We are all like camels,’ he said. ‘We need no food, only a little water to keep us going.’

There was no appeal or gratitude in Ali’s eyes, but no disgust either. He was not like the others she had treated, who looked at her – a woman – with a confused wash of fear and distaste. They squirmed, sometimes, told the interpreter they wanted a man. ‘There is no man. She treats you, you live. Or you can refuse and die.’

Ali’s wounds had not been not so severe, she recalled. Bone was incredibly strong. If a high-velocity bullet entered a body and hit a bone, it could be deflected, even if the bone itself were shattered. Then the bullet went on a zany trajectory, sometimes travelling up people’s forearm, through their shoulder, and out the other end, leaving its trail. If it failed to hit the soft tissue of a vital organ, the casualty might be saved.

There were other wounds, invisible, that only a surgeon would see. The kidney smashed into overripe watermelon, so that the flesh became almost granulated, slipped through her fingers with its ooze of juice and blood. When they hit organs, bullets pulped them. Then there were the bullets that kept on going through the body, having encountered no real resistance, shattering out the other side of a shoulder or an arm, taking with it a triangle of flesh, then carrying on into the body of the person behind them, passing through a shoulder or a neck again, penetrating the skin of a third. These bullets kept going for an average of 2.2 kilometres – another statistic her dry major boss had taught her, nearly ten years ago now, in Kandahar.

In Ali’s case there was a neat exit wound from an AK round which had skirted his abdomen and exited his back, tearing his lateral muscle but missing his spine. She had traced the bullet’s cavity, sewed the exit hole, and thought, that’s another one ticked off.

The following day she stopped by the recovery tent. Ali sat on the bed. She examined him and pronounced that he would be well enough to leave in two days’ time.

‘Thank you,’ he said, in his precise English. In one eye was an inquisitive, even kindly, expression. The other eye’s direction was random and interrogating. This astigmatism unnerved her. When she spoke to him sometimes she would focus on the left eye, sometimes the right. It was as if her mind refused to take him in all at once.

That afternoon she was stirring masala into a cup of tea when Andy called to her, telling her she had a visitor.

Ali hovered on the threshold of her office.

‘Would you like some tea?’ she said, in her best Arabic.

‘Thank you,’ he returned, in English.

‘Please, sit down.’ She offered him an orange plastic chair, regulation issue, coated in dust, like everything else.

He levered himself slowly onto the chair without wincing, but his pain was evident in the twitch of his deltoid.

‘You are not quite healed.’ She knew he was planning to leave the following day. They could do nothing to stop their patients sending a goat herder as a runner to the nearest village with a message to send a truck. In the old days they’d had to return people across the border or into frontlines beyond the field hospitals, a dangerous task.

‘I am well, thank you.’

‘I am glad to hear that. Allahu Akbar.’

He frowned. ‘Are you a Muslim?’

‘No, but I thank Allah for his grace.’

‘I wanted to ask you if I could listen to the BBC. It is where I learned my English, from the World Service. It would give me great pleasure to hear it again.’

‘I’m not sure I can do that.’

Ali lowered his cup and fixed her with a grave, certain look. ‘I only want to listen to the English.’

‘I believe you. But I don’t know if my director will.’

Ali put his cup down on the ground. ‘I thought you were in charge here.’

‘No, I’m only a doctor.’

They looked at each other. The formality of their conversation, the upright, manufactured tone of his supposed radio-learned English, the gravity of Ali’s eyes, were for a moment so overwhelming that it threatened to tip over into the absurd. She had to fight against an impulse to laugh. She might be a bit hysterical, with the heat, the hours, the pressure. She hadn’t laughed in a month.

‘You need to get your bandage changed. Go see Alan in the nurses’ tent. Announce yourself first. He is not expecting you.’

Ali smiled. ‘We are none of us expecting anything here.’

She watched him cross the courtyard. When he was out of sight she took out the notebook she carried in a money-belt-type pouch next to her body and wrote: Ali. Nom de guerre. Speaks English. One for AC?

Among the ten days he was in camp were days she would later forget. Or rather it was not that she forgot – each day was subtly different in the dilemmas it presented: a case of anemia, two children with rickets, an elderly man in the grip of malaria – but days when violence did not tear the fabric of their lives somehow failed to cohere in her mind.

‘You need to get into the habit of keeping a diary,’ Anthony had told her soon after their first meeting in London. ‘Make it a medical diary, but write anything that comes up in code. Decide on one – medicines, procedures, parts of human anatomy. I leave it up to you.’

She had enjoyed this part of her task. She decided on arteries for news she heard, anecdotally from her patients, or in her eavesdropping missions around camp: carotid artery presents oxygenated blood flow. Platelets advancing to hippocampus translated as: news heard that Al-Nur is advancing from the interior to the coastal capital, Port Al-Saidi. She came up with an emergency code consisting entirely of anti-malarials: chloroquine, atovaquone, progruanil hydrochloride, doxycycline.

It must have been later that week when she finished a repair job, not particularly challenging. Femoral artery of the left leg, frayed but not severed by metal shards from an exploded RPG. Shrapnel came in several disguises, but the blackened residue at the edges of ragged epidermis betrayed the culprit.

She peeled off her gloves and went to stand at the door of the tent. The sun fell on the perimeter of the tented verandah. She wanted to smoke, to drink, to stand on her head. But the nearest cigarette was two hundred and seventy kilometres away, and she didn’t smoke anyway. She tried to remember if a swash remained in the bottle of the contraband vodka she and her colleagues kept stashed under her bed, away from the breathalyser eyes of the Christian logistics organisation. She might have downed it the week before in a similar frenzy of remorse, she couldn’t remember.

A bustard – black bellied, she guessed, from the dark shadow on its underside – winged across the sky like a scar.

She went to visit Aisha. She had been living in the Vango tent for two weeks. She refused to speak to men, Andy had told her.

They sat cross-legged on the ground in the meagre shade thrown by a whistling thorn. The camel sat next to them, its long legs folded primly under its body.

‘Do you know about the Wir?’

La, she said. No.

‘You people call it luck,’ she said.

‘What is it then?’

Aisha thought for a moment. ‘Justice.’

She knew the word in Arabic – eadala. She knew that people who lived ruined lives clung to justice over luck. She could hardly blame them for being unconvinced that ordinary humans were responsible for their suffering

Two months before she had left England an expert from the School of Oriental and African Studies had come to speak to them, a strikingly handsome professor with dark malachite eyes. For the Bora and the Nisa alike, he’d told them, spirit possession meant being in the grip of an external force much more powerful than yourself. Attempts to tame or understand it were futile. For them, these forces represented not ecstasy, nor exorcism, nor possession, only a geometry of the soul and a restitution of order.

She’d worked in places in the grip of similar beliefs: spirit-dogs that stalked the living, harbouring souls of the dead; vultures that were actually someone or other’s great-grandfather given wings. Dark fortune lapped effortlessly at the edges of villages razed by rebel forces or visited by famine. She was chastened by the relentlessness of this moral system and she was too tired, these days, to challenge another culture’s shamanism. So she did not tell Aisha what she herself believed: that nothing else existed other than human order and morality, human cruelty and human chaos.

She lacked the Arabic to say all this, besides, she no longer had to be right, she no longer wanted to change things. She felt muted, she had felt this way for some time. She seemed to be entering a new phase of life. She was getting used to existence, finally. She felt the pleasant authority of maturity settle within her, but also, connected to it, something dulled, like old silver.

She excused herself and rose. Aisha smiled and thanked her for her visit. She had filled out, somewhat. Her vital signs and iron count had improved.

She walked towards her office. The wind picked up, ruffling the valence of the giant tent. She ought to do paperwork. She didn’t know why she was standing, looking out again into a land that gave nothing back, save for the edge of a burning column of setting sun.

Aisha’s camel levered himself to his feet at the same moment she had risen. He floated towards her. For him the sight of her had become the equivalent of passing a Sainsbury’s on a wet night. He plodded in her direction.

‘Aren’t you afraid of him?’ Andy had materialised beside her. ‘Camels are vicious buggers.’

‘Not this one.’ She waited until the camel filled their vision with his worn doormat nose and chocolate eyes. ‘I’ve named him Montague.’

Andy nodded. ‘He looks like a Montague.’

‘Stay still or he’ll know you’re afraid,’ she instructed. The camel’s long neck extended in Andy’s direction. Andy shrank back. She put a hand on the camel’s nose. Immediately his neck drooped. He uttered a low rumble.

‘You’ve gone right native,’ Andy said.

Andy left and Montague wandered back to the umbrella thorn he had been stripping of its leaves. Her eye caught a smudge in the sand near the operating theatre tent. Its glossy hue meant oil, diesel or blood. Possibly all three. The heat was thinning. In the sky was a watermelon sunset.

‘I’m sorry to disturb you.’

He stood in his white shirt and torn black trousers. His beard was immaculately trimmed and a pencil was shoved behind his ear. He looked like a village schoolmaster.

‘My people are coming to get me.’

‘You are not yet healed.’

‘This camp is not well defended.’

She stiffened. ‘Is that a warning?’

‘They might think that you will not give me up. I can’t communicate with them to tell them otherwise. I need a radio.’

‘I can’t.’

‘Are you a Shakespearean?’ he asked.

‘Not particularly. Why?’

‘I have a quotation that might interest you. Something I learned on the radio.’

A voice called her name with the sharp urgency of something gone wrong. She bolted. After two strides she turned back to Ali, but he had melted away behind her. She never discovered which play he was so eager to recite.