One

The numbers of people thinned out soon. It was disheartening to think that so few had made it. In terms of percentages dead, he couldn't know for sure, but after the ninety-nine and the decimal point, he was willing to bet there were lots more nines involved. By the time he reached the City Road he was on his own again, his shoes slapping echoes from a thin gruel of slush and ash. A pipe had burst underground; water was geysering from a crack at the southern end of Upper Street. He splashed through a small river at the mouth of the Tube station, struggling to pull back the barrier gates, their runners snagged in years of accumulated litter. He stood in the entrance hall, water sluicing past him, roaring down the escalators. It would be dark, properly dark, before he'd made it halfway down there. He thought there might have been a mistake. Of all the places people could choose to live, why here, in permanent night? He wondered if his exhortations to leave might not be understood. Too long out of the real world and everything shut down.

Chalk marks adorned the walls, all of them orange. Someone had scrawled Come and play. Jane went to the mouth of the escalators and peered down. He supposed the tunnel network offered a freedom that wasn't necessarily available on the surface. But he still would not swap the skin of the earth with the veins beneath it. Like veins, the tunnels would become more and more furred. There was structural collapse occurring all over the city. He didn't fancy being marooned between stations with flood water hammering towards him from both ends. Or a ceiling giving way. Or a fire breaking out. There was nobody to maintain the upkeep of the system any more. People choosing to come down here, he thought, descending the longest escalators in the entire network, were out of their minds.

At the base of the escalator he was groping blindly. His foot reached level ground and he stood still for a while, head cocked, listening for signs of life. Shapes began to become known to him: the edge of a wall, the outline of a maintenance doorway, the familiar London Underground roundel against white tiles. His scalp crept as he considered the possibility of Skinners, lots of them, standing mere feet away. But popular wisdom spoke of Skinners rarely sinking below street level. They didn't like the stink, some said. Or maybe there was some kind of interference with their internal compasses, an anomaly in the magnetic flow. Maybe they were confused by the various scents barrelling around the tunnels, pushed and pulled from unknowable sources any number of miles away. Maybe they were just smart, biding their time, knowing that the inevitable collapse of the honeycomb would send people running into their arms.

Jane gripped the rifle, holding it out in front of him as if it were a torch. As he neared the broad southbound platform, though, he saw that there were lights down here, albeit crude and lacking in power. Candles were dotted between sleeping bags and tents pitched all along the platform. Their uncertain light reflected in the scarred curve of the ceiling, showing how it had crumbled back to its supportive ribs. Posters on the trackside wall had peeled to the extent that nothing could be made out in their messages. Water sheened the walls; nitre was a series of slow white blossoms. A stench rose up from the latrine that the tracks had been turned into. He had to zip his coat up over his nose and mouth. 'Jesus,' he whispered. 'Mind the crap.'

People began to unfold from their beds, like insects shedding their chrysalides. Thin, shivering figures approached him, every one of them with eyes so large they seemed painful to carry in the cross-hatched wastelands of their faces. A woman touched his arm; the light of the candles gave her skin a pale, waxy sheen, as if she were assuming the form of what illumined her.

'Have you seen my little boy?' she asked. 'He's my only boy. I lost him a couple of months ago. He vanished in the night. I woke up and it was all I could do to convince myself I'd ever had a boy in the first place. Have you seen him?'

Jane shook his head and backed away. Scurvy was sinking her eyes, paling her skin; her hand on her lower stomach clutched at blood – the reopening of a Caesarean scar, he supposed. He could read chapters of pain on every face. They regarded him as if he was here to deal them the coup de grâce. Fear and resignation mixed to a pathetic uniform look.

He said, 'People are leaving London. You should too. There's a raft . . . a boat off the south-east coast that can take you across the Channel to France.'

His reading of the general mood was misplaced. A man with a white beard, his right arm bandaged and smelling of rot, thrust his chin at him. 'Why would we want to go to France?'