The first of them, the man the boy had arrived with, had reached the shore, and was climbing out of the surf. The others straggled behind him. Mary wiped her hand on her thigh and started after them, clambering over the rocks when the waves went down, stopping and holding on when they came up again and tried to wash her off.

She’d gone only a little way when she looked back. The turbaned kid hadn’t moved, still fixated on the blank slab they’d all emerged from. He reached out and put his hand against it, pushing at it and seeing if it was real.

‘Leave it,’ she called. ‘Leave it, okay?’

‘Where are we?’ he shouted back at her, repeating his earlier question. ‘Where?’

‘We’re not being burnt to death in some disused station corridor, that’s where.’ She turned her face to avoid a direct hit from a wave. ‘Did you want to stay there?’

‘No.’ He didn’t sound certain.

‘Then get your fucking arse in gear and get moving. The water’s getting higher and I’m not fucking drowning for you.’ She couldn’t swim. Float maybe, but not swim. If she got swept away, that’d be that, and it wouldn’t matter that she’d escaped the heat of the Underground that had claimed almost everyone else. So she moved faster, took more risks, received more knocks and scrapes, got everything wet.

And she was certain that she was still alive, that she wasn’t some hollowed-out twisted skeleton cooked so hard her bones had split open to the marrow. No, that wasn’t her. She was up to her belly button in water so cold she was losing the sense of feeling in her toes, climbing towards the shore along a line of rocks sharp enough to cut her.

Like the kid, she had no idea where she was, but unlike him, she didn’t much mind that she hadn’t gone the way of all the others. She’d survived, because that was what she was good at. She moved on, hand over hand. She was right about the rising height of the water. The line of rocks was disappearing, the waves topping them more and more regularly, covering them for longer, leaving her less time to make progress.

She made it. She reached a point where a strong hand came down and helped her up the last part, and on to a rock that wasn’t swamped with every wave. She climbed higher, well out of the wash, and finally got to sit with her back to the cliff. She was exhausted.

The kid struggled on. He’d almost left it too late, and the sea closed over his turban a couple of times. He re-emerged, spluttering and gasping, shaking the water from his eyes and resighting where he was heading.