But there wouldn’t be much more achieved tonight. It would soon be dark, and the activity around him was aimed at securing the scene for the night, ready for an early start in the morning. A vehicle manoeuvring in the woods already had its headlights on.

Then Cooper saw a movement on the opposite hillside. A figure was walking along the skyline, dark and indistinct against the grey cloud. Maybe there was a public footpath up there, he wasn’t sure. The figure kept moving, but Cooper was certain the eyes were turned towards Litton Foot and the unusual activity below. That would be natural, of course. Any passer-by would be curious. But wouldn’t it be more natural to stop and look, to puzzle for a while over the white scene suits and the police Land Rover reversing over the ridge? This walker did none of those things, but scanned the area efficiently in a few seconds, before vanishing behind a rocky outcrop.

Fry had seen the figure, too. ‘He’d be miles away before we could get to him,’ she said. ‘If that’s what you were thinking.’

‘When I saw him, I was wondering if the killer came back here to check on progress,’ said Cooper. ‘And what about the smell?’

‘There was no one here to smell it, Ben.’

‘I suppose not.’

He studied the hillside again. In an open location like this, the scent would have travelled. What were those gases produced by decomposition? Hydrogen sulphide and methane? They’d have drifted away from their source on any available air currents, forming cones and pools of scent, like invisible markers of death in the landscape. Depending on the weather, the smell might have lingered for days, or weeks. But wind and rain would have dissipated it quickly, so that anyone passing within a few yards of the remains might have noticed nothing. What a pity this wasn’t dog-walking country.

Then Cooper frowned and looked back down the hill towards Litton Foot. Tom Jarvis’s house wasn’t visible from here. It was in the bottom of the dale, and the woods were thick in between. But Jarvis’s dogs had run in those woods before the new fence had gone up, hadn’t they?

Or rather, one of his dogs had.

Then one of the SOCOs called Cooper over to the edge of a patch of bracken a few feet from the location of the remains. ‘Look at this –’

‘What have you found?’

‘See for yourself. But don’t get too close.’

Cooper moved a little nearer. ‘It’s a gin trap,’ he said.

‘It looks a bit rusty. I don’t suppose it’s in working order.’

‘It’s meant to look like that.’

‘What do you mean?’

‘You’re supposed to let a trap develop a coating of rust to disguise it. It gives the steel a neutral smell, so as not to put animals on the alert.’