One

Although the fuselage had disintegrated, there were sections of the interior that had survived the impact. Some passengers were strapped into their seats, bolted to the floor. One man, decapitated, held on to a plastic cup, imprisoned between clenched fingers. Most of the bodies, or body parts, lay in the field; some had hit with such force that they had partially buried themselves. Suitcases and handbags, wheelchairs and buggies. Someone had once told him that whenever you took a flight, the chances were there was a coffin in the hold. The shining dust from the crash skirled around the debris as if reluctant to leave the construct that had produced it.

Aidan had found a laminated emergency procedure sheet. He stared at it for a long time before tucking it under his arm. He seemed thoughtful, as if he'd done something wrong. Looking at children sometimes, Jane thought, you could almost see the cogs shifting.

They found what remained of the cockpit: instrument panels and throttle levers, the pilot's chair. Miles of wire and hydraulic cables hanging out of bulkheads, like some lost ungodly page from Gray's Anatomy. Nothing of use. Everything in the galleys broken or crushed. Jane found an ugly mass of metal and a great deal of blood but couldn't work out what it was. There were hard impact marks – deep scars in steel – that suggested there had been some almighty meeting of surfaces. He saw the edge of a small plastic number plate and realised: the seats at the front of the aircraft, maybe four or five rows, had concertinaed into a compressed block barely a foot deep. There were people crushed paper-thin inside that. He saw tufts of hair. Little else, thank God.

'I've seen enough,' he said. They went back to Becky, who was playing with her bracelet, staring resolutely at the ground.

'Think of how many aircraft are in the skies at any one time,' she said, and he saw her shudder, an almost reptilian reaction that moved slowly through her body from her head to her feet. It was as if she were trying to slough her skin. 'There's just no end to this. No end at all to how low things can get. No end in sight.'

Jane didn't know what to say. He muttered some bland platitude about survival, how she had to go on because she had no choice. But he didn't really believe it. She stood up. She had either swallowed what he had to say – which he doubted – or decided to move on anyway. It was all for Aidan. Jane wondered what she might do if the boy wasn't there. He felt almost guilty that he had Stanley to keep him motivated. How empty was your own life if you had nobody living in it?

The three of them picked their way through the wreckage and put the M25 behind them. They were within its circle now, and Jane knew that somewhere within its borders, somewhere within this 800 square miles, was Stanley. He thought it would give his gait added swing, but instead he felt more and more enervated. He couldn't concentrate on anything but that great circular concrete road, how it seemed like a trap, a slip-knot that might close around them at any moment, trapping them for ever.

They bade farewell to the A1 where its motorway namesake crossed beneath it. They headed south-west across Edgware to the A5, the ancient Roman Road that would lead them, straight as a rule, to Marble Arch. The nearer Jane got to his goal, the slower the going. The bodies had been increasing in number ever since they passed into the northern environs of the city. In some places they had to double back and find a different route; it seemed as though every person in the street had come together in a mass huddle to die.

Jane tried to leaven the atmosphere with jokes, but his delivery was exhausted, deadpan. He looked into Aidan's grey emaciated face and saw himself there. Nothing for the boy to grow into; he was old before his time. Where could you go from here? Back to Toytown and Sodor and Nutwood? What was there in those places for a boy who had seen heads without faces; death in every possible position and permutation? You couldn't reclaim your youth after that, no matter that it was only a third lived.

He had to gee Aidan along; he was complaining of being tired. 'We're nearly there,' he said. 'Stanley. He's going to love you. You two are going to be great mates.'

'What if he's dead?'

Jane's stride faltered. Becky said: 'Aidan.'

'It's OK, Becky,' Jane said. And to Aidan: 'He's not dead.'

'How do you know? Everyone else is.'

'You're not. Becky's not. I'm not.'

'Everyone else is.'

'I can't explain it to you,' Jane said. 'I can't make you see. But he's not dead. I promise you. Now let's get cracking. Get a wiggle on.'