‘Command think Peralta’s got his hands on some kind of nerve agent,’ explained Nirav. ‘That means everyone gets a shot, and we also take a blood and DNA sample at the same time. Everyone has to do it, no exceptions.’

Nathan glanced warily towards the doctor. ‘Forget it. No samples of any kind, either.’

‘Why the fuck not?’ asked Karen.

‘Sorry,’ said the doctor, patting a pocket. ‘Got that already while you were out cold. So how about you stop whining and take the shot now, so I don’t have to get some of the guys from security to come here and hold you down while I give it to you anyway?’

He hesitated, and even thought about making a run for it and taking his chances outside before they could identify him from his DNA sample. But where could he go? His work as a medic had given him a sobering overview of just how bad things were in the city; outside lay only a cold and hungry death.

Instead he nodded, and Nirav pressed something cold against his neck. There was a hiss and a sudden jolt of pressure against his skin, and then it was over.

A block of ice immediately settled into the pit of his stomach. It had only ever really been a matter of time before they worked out who he was, and there was literally nowhere he could run.

As Nirav departed, Karen folded her arms and studied him with a mixture of motherly concern and mild contempt. ‘To be honest, Nathan, after the way you ran off back there, I was worried maybe you’d caught a whiff of that nerve gas and gone crazy. Who was it you said you saw?’

Nathan shook his head. ‘I made a mistake.’

She sighed and reached out to tug him closer to her. ‘How awake are you?’

‘Not very.’

She shook her head. ‘Not the right answer,’ she said, pushing a hand through his hair. ‘It’s been a long day, Nathan. Let’s go back to my place.’

What Karen called ‘her place’ was a room in a commandeered administrative block on the other side of the main refugee camp. She had cleared it of most of its remaining furniture, whatever hadn’t already been burned or looted, and had installed a spare cot from the clinic. Technically this was against the rules, but nobody seemed to care enough to enforce them. The illicit arrangement did have the advantage of giving her and Nathan some privacy.

A small portable heater glowed in the dark nearby, illuminating Karen’s warm lithe body from behind her. Nathan slid his hands around her waist, then moved them up to cup her small breasts. Her tongue felt wet and salty as it licked against his lips. He felt himself stiffen, a wave of sudden, needful ardour washing over him.