One of the later extensions to the mill had been converted into a car park. Cooper drove up a ramp and parked on the roof near a side entrance to the shopping village. Over the wall, he could see the convex weir built to take advantage of an outcrop of rock on the opposite bank of the river. From there, the water ran into a goyt, the fast-flowing channel that had driven the mill’s waterwheels.

‘What are we looking for here, Ben?’

‘Eva Hooper. She runs a retail unit on the road level.’

Murfin opened the door into the shops. ‘Mmm, cakes.’

There were four open-plan retail levels, accessed from a central staircase like an old-fashioned department store. Each floor was divided into areas selling discount designer clothes, furniture, food, golf equipment. The mill clock was still on the wall at road level, but for some reason it had stopped at twelve noon. On the lowest level was a restaurant, lined with windows overlooking the river. A patch of brown scum had formed on the water, as if a few gallons of coffee had been spilled there.

‘Gavin, why don’t you find the offices and ask about CCTV footage? There’s a camera over the main entrance.’

‘All right.’

Cooper had seen signs on this floor for the working textile museum. Could it have been part of Miss Shepherd’s afternoon out, before her visit to the aquarium? Perhaps Arkwright’s legacy had some significance for her. Come to think of it, she was old enough to have worked here at the mill. Had she been revisiting old haunts, re-living memories one last time?

Cooper shook himself. He’d begun to imagine the victim having some kind of premonition that she was about to die. But no one knew the time of their death in advance, unless they had some terminal illness. Or they were intending to commit suicide. That was the only way to be really sure.

The museum was reached by leaving the shopping area and passing through an echoey room over uneven wooden floors that creaked and shifted underfoot, worn by decades of use by Arkwright’s millworkers. Bobbins and shuttles were on sale here, along with other mementoes of the textile industry that had once employed so many.

He found a man taking money on a flight of stairs that led down into the spinning and weaving sheds.

‘Do you issue admission tickets here?’ he asked.

‘No. You get a leaflet with a map of the route through the rooms of the museum – see?’

‘Were you working on Saturday?’

‘In the afternoon.’

‘Do you remember this woman coming in?’

The man looked at Cooper’s photograph.

‘No, sorry.’