Laura watched her as she ran past, transfixed for a moment by Rachel’s ponytail as it swished along the back of her Lycra vest, her shoulders muscular, a bottle of water in one hand, the small white wires of her headphones connected to a music player that was clipped on to a band around her arm.

Laura looked away. She didn’t need to see Rachel’s pert little arse to remind her that she wasn’t in the shape she ought to be. Laura glanced at herself in the rear view mirror. Those laughter lines didn’t disappear anymore. The memory of her last run came back to her and she shuddered.

Rachel appeared in the rear view mirror. The sun was getting low and so she had to squint as the evening rays put everything into silhouette.

She put her car into gear and set off. She glanced down the side streets as she drove, those that headed towards the canal, and then came to a stop at the next junction. She was looking along the road, waiting for a gap, when something troubled her, just a sense that she shouldn’t go on. Had she seen something in one of the empty side streets? She rewound her journey in her mind and tried to sift through the images. All she’d passed were long strips of industrial units, some large warehouses with lorries parked behind high fences, some small square brick blocks. But she had seen something, she knew it.

She checked her watch. She needed to get back to the police station, and she was about to shake off her doubts and start driving again, but she stopped herself. Being a cop was about instinct, about running with the gut feeling, and her gut feeling was telling her that something wasn’t right.

Laura sensed movement behind her, and so her eyes shot to her mirror. There was a van, small and brown, just nudging out from one of the side streets, just the front wing visible. As soon as she saw it, the bad memory rushed at her. It was the colour, drab and dull, with the pitted signs of rust near the headlight. Her mouth went dry, her palms slick on the steering wheel. It was the van that had almost knocked her over during her run.

It seemed like it was waiting, exhaust fumes drifting forward. Was it following her? Laura realised now what she had seen as she went past the side streets. It had been the van, parked further along, facing the canal. How long had it been there? If it was following her, how long had it been following her for? She looked down into the door pocket, to see whether there was anything she could use as a weapon. Nothing.

She clicked on her phone, her hands shaking as she selected the hands-free option.

‘Joe, he’s here.’ Laura tried to speak calmly but her breathing was shallow, the adrenaline flooding into her veins.

‘Who’s here?’

‘The man in the van. The emailer. He’s behind me.’

‘Where are you?’

‘I’m by the canal,’ she said. ‘Pendle Street.’

‘Keep driving normally,’ he said. ‘Make him follow you. Keep a commentary. We’ll get someone there.’

She set off slowly, watching in her rear view mirror all the time. The van stayed in the junction, just waiting, trails of fumes drifting forward. Her hands gripped the steering wheel, waiting for it to pull out, but then it set off and turned to go in the opposite direction. Then she saw it again, the missing number plate.

The van blew smoke as it went, obscuring the rear window. She watched it crawl slowly to a bend further along that would take it away from the canal. As she saw it go out of sight, she caught a final glimpse of Rachel as she went along the towpath, just the tip of her blonde hair bobbing up and down.

‘Joe, it’s gone the other way.’

‘We’ve got cars coming to you.’

‘Rachel is that way.’

‘What way?’

‘She’s jogging. He’s followed her.’

‘Shit! Try and get to her, warn her.’

‘Okay, I’m following,’ she said, and turned the car around in the road, thinking about the route, about where it would come out.

The road followed the line of the canal mostly, a remnant of the days when it passed the front of the old mills and wharfs. It was a quieter route now, because the thing that had kept the canal in business so long – the cotton industry – had died, leaving just patches of open land and the occasional derelict building. There were new houses further along that had been mocked up to look like stone cottages but that was about it, the regeneration creeping slowly along the waterfront.

Laura set off in the direction of the van, wanting to get behind it but not wanting to spook the driver. She tried to see along the towpath, to check that Rachel was still there, but the canal curved away, so that she couldn’t see much more than twenty yards ahead. She looked along the road. Laura thought that it returned to the canalside around half a mile further along, just before the houses started.

She followed the road round, past the shells of old mills, the roofs crumbled to just trestles, the windows sealed shut with metal plates to keep people away. But people still found a way in, and so the metal shutters hung a bit loose, and Laura guessed that the inside would be littered with discarded needles and old beer cans.

As the road curved back round to the canal, Laura felt a jolt. She couldn’t see the van. She should have caught it up by now. And where was Rachel? She should have appeared by now too. What if she had stopped for a rest? Or would she be further along and almost home?

As the road got closer to the canal, Laura saw that there was a place to park in front of some old wooden bollards, now almost covered by trailing blackberry bushes. Laura climbed out of the car and looked around. The streets were deserted, the evening rush hour gone, and so all she had were shadows as she tried to get her bearings. She was nervous, aware of how deserted it was. She stopped by the bank and looked along both ways, her feet making soft crunches in the gravel as she turned, but it seemed loud as the sound bounced off the water and the high wall on the other side. What would she say if Rachel appeared around the bend? Except that Rachel didn’t appear. There was no other sound, apart from the soft brush of trailing branches along the canal surface, the only ripple in the dark ribbon of water that curved round to the heavy black lock-gates Laura could see in the distance. Rachel could not have got that far ahead, not in the time she had.

Laura turned around, unsure what to do, waiting for the wail of sirens.

Then she heard a noise, like a scream and a bang.

Laura tracked the noise, her senses heightened. It had come from further back, from the direction she had come from. Laura moved slowly along the towpath, looking for shadows moving in the bushes that grew over it, waiting for an attack. She wished that she had brought a pepper spray with her. The towpath ran alongside a patch of open ground and an old factory further along, with holes in the roof and the windows like all the rest, made tight by metal plates.

Her ears were keen as she went, listening out. There were some bushes ahead, and long branches that trailed forward, but she knew that the noise had come from further away. She kept on walking, swatting away the midges that were enjoying the final strains of daylight. The old factory was a hundred yards further along, but all she could hear was the slow crunch of her feet and the nervous rasps of her breaths. She could feel her heartbeat, like someone tapping on her chest.

Then she saw it, the van, the back corner just visible behind the factory.

Laura ran, every cell in her body telling her that something wasn’t right. Her breaths came faster, adrenaline coursing through her, as she strained to get to the factory.

She threw herself against the factory wall, all in shadow, and looked along the brickwork. She was closer to the van now and so she knew that it was the same one. She wiped her forehead with her hand, slick with sweat from the exertion. Laura crept along, her back pressed against the wall, trying to keep her breaths quiet, her phone in her hand, ready to dial as soon as she saw something to report. The bricks were cold through her shirt, her back clammy, and the ground was uneven and littered with old cigarette ends and beer cans. There was a bag on the ground nearby that looked like it might have once had glue inside. She tried to be as quiet as possible, her footsteps just light squeaks on damp grass, and when she got to the end of the wall, she put her head round slowly. The van was there, the engine off, the doors closed.