Sally had been thinking about murder for a while now. Not all the time, just off and on when the mood took her. Sometimes it would be when she was in bed at night, trying to get to sleep but finding herself staring at the bedroom ceiling for hours, while the weight of her husband’s comatose body dragged the duvet off her again. Or it might be while she was driving, frustrated by the traffic, hearing his parting words repeating in her mind over and over. Those were the times when she fantasised about finally putting an end to it all. It would be a kindness really.

She’d once heard someone claim that the best way to commit a murder and get away with it was to lure your victim up on to a high place, such as a cliff. As long as there were no eyewitnesses, it was almost impossible to prove from forensic evidence whether that person fell or was pushed. The fall had to be terminal, and unobserved. It needed to happen at a time when no one else was around.

But there was someone else here. Sally had been absorbed in such a world of her own that the sudden realisation came as a shock.

‘Did you hear that?’ she said.

Geoff had already stopped, his head tilted on one side. ‘I’m not sure.’

‘I thought there was something—’

He’d obviously heard the same thing, but Sally saw that he couldn’t bring himself to agree with her, even now.

‘Perhaps we should go back,’ he said instead.

And that was typical. He wouldn’t get into an argument, but would make it seem as though whatever they did next was entirely his own idea.

Geoff and Sally Naden turned back and began to walk up the track. They knew someone was nearby, and it made them nervous. Sally was still sure she was right. But this wasn’t the way it was supposed to be.

Just before six o’clock, Poppy Mellor was sitting in her car, parked against a stone wall on the Staffordshire side of the river.

Earlier that afternoon she’d been for a trip with some friends to Monkey Forest in Trentham. She’d always had an interest in apes and monkeys. And those forty acres of land south of Stoke were the only place in the country you could see them roaming free. A hundred and forty Barbary macaques in a Staffordshire woodland were the closest she could get, until she’d saved enough money for a trip to North Africa. Up in the Atlas Mountains of Morocco, that was where the macaques came from.

Poppy gazed down the slope at the dripping trees and bare fields. The Atlas Mountains were a bit different from the borders of Staffordshire and Derbyshire, she imagined.

She’d been sitting in her car for a few minutes thinking about the noise. She was in the middle of reading a text message from Imogen, one of her friends from the drama studies course at uni. Her dad would raise his eyebrows at the idea of her texting someone she’d seen only a few hours before. He would say it was a kind of compulsion. But she always felt this need to be in touch.

Those monkeys at Trentham lived in close family groups. She loved them for that. Whenever you saw them, they were either physically touching or talking to each other, sometimes both. Their hierarchy was complex too, though she supposed one always had to be the leader. Every macaque knew its role, and they could rely on each other totally for loyalty and support.

Poppy sighed. Humans had a lot to learn from other primates. She ought to tell her dad that. She could just picture his face now. Some people’s reactions were so predictable. For months she’d longed for something to happen that would make her life more interesting.

She turned up her CD player and wondered if anyone had heard that scream. There were lots of strange noises out in the country at night. It could have been a fox, perhaps? It was mating season and vixens called like that sometimes.

But Poppy knew it hadn’t been a fox. Even from a distance, it had unmistakably been a primate. Or more specifically, human.

Further down the slope, on either side of the bridge, Jason Shaw and the Nadens were unaware of Poppy’s presence. Jason peered cautiously into the trees as he climbed the slope, stopped, walked a few yards into the undergrowth, then changed his mind and came back again.

Three hundred yards away, Poppy had got out of her car. She glanced for a moment at the clouds scudding overhead, revealing brief glimpses of the moon, still pale against the twilight blue sky. Then she leaned on the stone wall and gazed down into the valley where the river ran through the darkening woods. Her eyesight was good, but she could see no movement, no sign of any human presence among the trees. Poppy thought of making a phone call, but knew it would be pointless. So she got back in her car, switched on the headlights and accelerated away down the road towards Hartington. The Nadens took longer to reach their home, after stopping to argue about the best route to take.

None of them would forget that night for a long time. Though, in the end, it was someone else who found the body.

2

Detective Sergeant Ben Cooper was still sleeping badly. He’d been relying on the help of tablets for months now, switching from herbal aids to chemicals and back again, fearing that he’d get too reliant on some particular substance and would never be able to sleep without it again.

But this particular night had been full of demons and ghosts. And many other creatures too. Vampires, witches, skeletons. And hordes of stumbling, bloodied zombies like the entire cast of extras from The Walking Dead.

Well, it was always like this on Halloween. By twilight the streets of Edendale had been full of groups of children in home-made costumes fashioned from plastic bin liners and toilet rolls. After them came the teenagers with their supermarket horror masks and pumpkin lanterns. Later the atmosphere changed as the pubs filled with flesh-eating monsters, their prosthetic fangs dripping with gore. All in the name of harmless fun.

So Cooper was awake at 2 a.m. From his ground-floor flat in Welbeck Street, he could hear the distant sounds of revelry from the pubs in Edendale town centre, just across the river. Though revelry was a kind word for it.

‘Harmless fun,’ he said with a sardonic laugh, breaking the silence of his flat.

There were police officers on duty out there, some of his E Division uniformed colleagues from West Street, assigned to the drunk shift. They would have been shivering in their vans for the past couple of hours, waiting for the bars to empty and the fights to start.

In the old days, before the formation of professional police forces, the duties of watchmen had included firefighting and sweeping the excrement from the street. Many officers would say they were still doing the same thing now.

Edendale wasn’t much different on a Thursday, Friday or Saturday night from any other town up and down Britain. Halloween just meant the prisoner cages would be full of battered Draculas and legless Egyptian mummies. Fake blood would be mingling with the real stuff. And the pavements would be littered with the dead, staggering towards home.

‘And do it quietly, please,’ said Cooper. ‘Like a good zombie.’

He was glad no one could hear him. He’d always thought people who talked to themselves were definitely a bit weird.

Cooper looked around for the cat, but found her asleep, curled up by a radiator. She was probably aware of his presence, but too wise to think it might be breakfast time so early. She’d grown used to his erratic hours over the last few months and refused to let his unpredictable behaviour affect her routine. Lucky animal. She seemed oblivious to the noise outside too, except for a twitch of an ear if someone passed too close in the street. Occasionally, there was a wandering ghoul, lost and drunk, clattering down the road and vomiting in the gutter.