Owen Fox had completed the first course of stones and had begun sliding the big throughs back into the wall. The throughs would hold the whole structure firmly together. With these and the topping stones in place, the wall would stand for another hundred years or so.

‘Why would a man do that? Attack all those women?’ asked Mark Roper. ‘What would he be thinking of?’

Owen didn’t pause in his work. ‘I don’t suppose thinking came into it,’ he said.

‘What then?’

‘I think it would be a physical thing. An instinct that the mind has no control over.’

Mark considered this, and nodded. ‘I know what you mean.’

It seemed to Mark Roper that Owen was like a stone wall himself, solid and reliable, calm and controlled. He never raised his voice. But then, Mark’s father had never raised his voice, either. He had never smacked, or even criticized – not that Mark could remember. Instead, he had joked all the time, and talked about all sorts of subjects. His father had loved to make things. He collected useful bits of wood which he would never get round to doing anything with. He used to drive his mother mad by stopping the car to pick up a broken piece of pipe or a sheet of corrugated Perspex from the side of the road, or a wooden crate fallen from a lorry.

But his temper had changed after Rick had died. And Mark’s parents had drifted apart instead of supporting each other, until his father had moved out. And then there had been the new man.

Mark could see the stones in the completed length of wall were bonded like brickwork, laid across the joints in the course below. Every stone touched all its neighbours, allowing no room for movement. They were wedged in tight, each with its own role and no possibility of shifting without a danger of bringing down the entire structure. In this part of the world, there were whole villages made like that, thought Mark – not just the houses, but the people too. You weren’t allowed to wander out of line. There was no room for movement, no shifting from your allotted role. Wedged in tight.

Clumsily, Mark tried to express this thought to Owen. The Area Ranger listened to him for a few moments, then rubbed a hand through his beard.

‘You haven’t come across a suicide yet, have you, Mark?’ he said, as if picking up the thread of an entirely different conversation.

‘No.’

‘You will, in this job. I think suicides are the saddest deaths of all. It means someone has decided that life has no part for them to play any more.’