An artist had set his easel up on the bridge, trying to capture the scene downriver towards the Pavilion, with trees reflected in the moving water. Cooper often came across painters, though usually in the summer. He had to admire the effort they put in, if only to carry their equipment from the car. But they were setting themselves a hopeless challenge. This landscape was constantly changing. No set of watercolours was going to preserve it on a canvas.

He noticed that Life in a Lens stood on the other side of the aquarium, with a Victorian tea room on the ground floor. This was his chance to call in and ask about the webcam.

When he came out a few minutes later, a school party was queuing to enter the mining museum further down the road. There were two cameras on the outside wall nearby, but they were focused on the entrance to Brody’s nightclub. When he was a teenager, Brody’s had been known to the local kids as ‘The Pav’, because it was located on the upper floor of the Pavilion, above the mining museum and the tourist information centre.

But where the heck was Gavin Murfin? Cooper stood by his Toyota for a while, looking up and down the street. Then he walked a few yards along South Parade, past the ice-cream parlour and the antiques centre to the corner, where he found that a science-fiction bookshop he remembered had closed down. He supposed it had been a mistake to let Gavin take the interview with the waitress at the tea rooms. The smell of fish and chips on the promenade was so inescapable that he must be giddy with hunger by now.

Finally, Cooper pulled out his phone and called Gavin’s number. Strangely, the ringing tone seemed to be echoed by a tune playing somewhere nearby. He turned and looked into the windows of the building behind him. There was Gavin, eating a choc ice. And waving.

‘OK, I did the waitress at the Riber Tea Rooms,’ said Murfin when Cooper got him away from his choc ice. ‘Nice lass, name of Tina. Get this – reckons she saw Rose Shepherd talking to two other people at a table in the café on Saturday afternoon.’

‘Wow, you got more than I did,’ said Cooper.

‘That’s why I thought I deserved a reward.’

‘What time was this, Gavin?’

‘Around two thirty, she thinks.’

‘That must have been after Miss Shepherd came out of the aquarium.’

Murfin used the tip of one finger to wipe a bit of chocolate from his front teeth. ‘I chatted Tina up a bit, and I got her to do her best with descriptions. But the tea rooms were full that afternoon. She did say the woman she recognized from the paper was wearing a dark jacket.’

‘That fits. What about the other two?’