‘I’m not responsible for whether it makes sense,’ said Fry. ‘I’m just sharing information, right?’

‘Fine.’

Cooper watched them drive off, then waited for Weenink to come back with their own car.

‘Where to now, Ben?’ he said.

‘Up there.’

‘What? Ben, do you know it’s Monday? I’ll be missing drinking time soon.’

‘Are you coming, or what?’

Weenink locked the car again. ‘Yes. But only because you’re not safe on your own.’

When they reached the Cat Stones, Cooper instinctively followed Diane Fry’s footsteps to the place where the attack on Maggie Crew was supposed to have taken place. He could see straight away what she meant about the leaves. No trees grew on the exposed gritstone edge.

‘Why shouldn’t it be here?’ said Weenink. ‘She might have been walking through the leaves earlier. She could have gone through them on the way up.’

‘Possibly.’

Weenink began to get impatient. ‘Ben, there are things to do.’

‘Let’s try this way a bit.’

‘But bloody hell –’

Cooper turned angrily. ‘Todd – just keep out of it!’ His face felt flushed. It was only a moment’s loss of control, but nagging doubts had made him irritable, and exasperation with himself was eating at him.

He worked his way north, as Fry had done. Weenink sat on a rock and watched him, like a tolerant parent. After a minute or two, Cooper reached the spot where the rocks parted, and he could see down to Rowsley and the railway line. The last train had gone, but he could see where the line ran. Which way had Maggie’s attacker come from? Not from the other side of the rocks, that was sure – not unless he was Spiderman. The slope behind him was steep, too, and covered in loose stones that would be noisy and difficult to negotiate. If you were going to run at someone at speed and take them by surprise, there was only one way to do it – downhill. People had known that ever since violence had been invented. That was why Iron Age forts were built on the summits of steep hills.

There was more dead foliage on the ground near the Hammond Tower, certainly. But how much would there have been seven weeks ago?

Then, in front of the tower, Cooper suddenly stepped into a hidden hollow filled with wet drifts of leaves. They lay in layers, where they had collected over the years. Below the surface, the older material was black and slimy and decaying into mould. You could wade through this lot, if you wanted to, and be very vulnerable to someone approaching from above.