‘Stop, Karl. I can’t see.’

‘It’s fine, just keep going straight.’

‘I don’t know where straight is. Where are we? Just stop, will you, please?’

‘We can’t stop. They might come down after us. Come on.’

‘No! Stop. Where does this go?’

‘Away from those bastards, and that’s good.’

‘STOP!’

He was far ahead. He stopped in his tracks and turned. In the dark, he could barely make her out. His urge to leave her behind was centre stage, but he knew he couldn’t. He had a daft vision of getting out of there and running into her husband, and having to tell him he’d left the man’s wife in the dark underground, torn, bloody feet and all.

But they couldn’t afford to dawdle. She was moving slowly and carefully because she was unaware of what lay before them.

‘We have to get out, and that means moving forward. So, hurry up or I’ll leave you here.’

She gasped in shock. He regretted what he’d said and apologised. ‘But we have to go. Move faster. You want them to catch us down here?’ He turned away. Arms out before him, like a kid playing zombie, he continued to move.

‘We’re trapped. It’s madness to move further – ow!’

Karl stopped as he heard Liz hit the ground with a thump. In the blackness, he moved back, feeling. Found her breast and quickly shifted his hands to her arm, cheeks flushing in the dark. Felt along until he had her hand and lifted her to her feet. He moved away, but kept hold of her hand. Still she wouldn’t move.

‘It’s okay. Come on.’

‘My feet,’ she moaned.

He remembered: she’d lost her shoes while climbing onto the roof.

He took his off, and felt for her toes. She said nothing as he slipped his shoes onto her feet, tying the laces as tight as he possibly could.

‘Come on.’

‘What about your feet?’ she asked.

‘Come on.’ Like coaxing a kid. He was getting in some practice. But he wouldn’t need it if they never got out of here. He wanted to shout to get her moving. He wanted to damn well drag her. He needed to get back to his family. The men after Liz hadn’t had a change of will with the new dawn. If they had decided to visit the shop then there was no reason they wouldn’t go back to his house. The thought terrified him.

But he didn’t shout at Liz. Instead he mustered all his restraint and said: ‘Come on.’

He gave her a gentle tug, and she moved. They walked with careful steps. They got four or five, and something brushed the top of his shoulder. Two seconds later, he heard her cry out again and jerk back, and she almost took his entire arm with her.

‘What?’ he hissed as he stumbled.

Her grey form dropped to its knees. ‘Something hit me.’

He took a step, and the thing that had brushed his shoulder hit him in the cheek and chest. He felt for it: a length of wood poking down from the ceiling.

‘We’re going back,’ she moaned. She got up, arms feeling out before her. Her fingers slipped over his face like giant spiders, then she turned, took a step back the way they came, and fell again, this time forwards. A thud, a grunt of pain. And tears. He saw her throw something from the ground, heard it slap a wall. The brick that had tripped her.

‘Where the hell are we?’

‘The builders posted a letter to all the shops, warning us about possible subsidence. They were digging up the buildings on this land and found a tunnel.’

With his eyes now fully adjusted to the dark, he saw her face turn to him. He held out a hand. She didn’t take it. Just sat there defeated.

‘It used to be connected to Victoria Park Station, up north about a mile. Vic Park closed in the forties. The overground lines and station were demolished in the 1960s when they built the East Cross Route.’

Comforted some, she took his outstretched hand.

He bent down, and pressed her hand towards the ground, and closed her fingers around the very thing she had tripped over. A steel rail.

‘It’s… it’s an underground train track?’

‘Not the London Underground, either, but a real railway. Something to do with an extension to some line or other. Long disused. I guess they were going to just forget about this underground section, let people in the future find it and wonder what life was like back when humans couldn’t teleport everywhere, but the post-Olympics regeneration of this area unearthed it.’

‘And we can follow this and… get out?’

‘The nearest station was Old Ford, only 500 feet from here, behind us. There’s a housing estate there now, though, and the route was filled in years ago. The good news is that this underground section exists all the way to Springfield Station. So, we can go forward. Springfield is also disused, but still there, and there should be a way up. I read that it’s close to West Ham Station, which is about two miles. But that will be two miles in the dark.’

‘Are you sure there will be a station?’

‘I saw plans of the tunnel and stuff. I looked them up once those builders told me about it. It was enough to postpone their building work while they checked it out. I wanted to make sure my shop wasn’t going to fall into the ground.’

‘So, we just walk straight on? What’s ahead of us? What if it’s a dead end and we have to go back and they’re waiting for us?’

He didn’t know how to answer that. The two men hadn’t tried to follow them, so maybe that meant they assumed Karl and Liz had fled above ground in the smoke. Surely they wouldn’t be lurking up there, waiting. It didn’t matter, anyway, because they were not going back. They would find a way out ahead of them somehow.

‘This is weird,’ Liz said. ‘Underground station. Like something from Tomb Raider. But what if the station is all bricked up and there’s no way out?’

He bit back a sarcastic joke. ‘There will be.’ He pulled her to her feet, and she came willingly.

‘Walk straight and you won’t trip.’

‘What if a train comes?’

She was making a joke now. To his surprise, he laughed. ‘You know trains. Always late. We’re fine. Come on. Keep hold of my hand.’

She gripped his hand tightly. Over-tight, which he took to mean she didn’t fully trust this plan. Nothing he could do about that because he didn’t fully believe in it himself. He took a step, expecting resistance from her. But she came.

‘Did you know that second man?’ he asked. ‘The one in the car? Was he the guy who chased you last night?’

‘I don’t know. I think he was a different man. The way he moved, and he was bigger. But he was hiding his face, so maybe he thinks we might have recognised him. Did you?’

He shook his head, then realised his error and vocalised his answer. ‘But he looked like he was in control. Like, if there’s a team, he might be the boss.’

They fell silent for a while. Karl tried not to think about that word he had used: team. The idea of many men after him was terrifying.

They walked between the tracks, taking smaller steps to keep their feet on the sleepers; it made Karl remember doing this as a kid with his friends. Long strolls along the train tracks, where it was peaceful. In Sunday sunshine, not crushing blackness. Something he hoped to do with his own son – or daughter – one day. They walked slowly, for a minute, in silence. By then, his eyes had adjusted to the gloom and he could see arcs and lines of lighter black in the dark. He could see the curve of the roof and the walls. And thin, long lines of grey-black that were the tracks they walked between.

And a fork. The tunnel split like a lizard’s tongue. One black hole on the left, and one black hole on the right, and nothing to distinguish between them except the track vanished down the right-hand route. Life and death choices had been made on less, so he chose the track.

But all his mind’s eye saw was Katie. He wished he’d gone home. She would be awaiting his call, but his phone was in the shop, a billion miles away, and she would begin to worry soon. He hoped his lack of contact would make her understand the threat they faced and force her out of the house, to her father’s place, which surely the men after them didn’t know the location of. She would call the police first, hopefully. But there was always a chance that she would remain in the house, waiting for the phone to ring – where the bad guys could be headed right now.

His pace quickened. Her grip tightened again, as if she feared he’d slip away. But then she said something.

‘Are you going to tell your wife you touched another woman’s breast today?’

He realised she wasn’t scared of losing him at all. Maybe she had sensed his growing unease due to his increased pace, and she was trying to shift his attention, to lighten the mood. Even amid her own fear and worry, she was trying to ease his anguish. It didn’t, of course, but he stopped and turned to her. Their faces were just inches apart. He wanted to try to ease her pain in return, but no words came.

That was when they heard a noise. Faint. It rolled towards them, and past, and was gone. Karl looked up and over her head, and Liz turned away from him, and they both stared back the way they’d come. The world was black, but way in the distance was a pinprick of light. Like a solitary star in the night sky. Someone had found their entrance.

Someone had entered their world in pursuit.