Nick left the hotel early and was at Porthtowan by nine o’clock. The village seemed deserted, though the morning was bright, the sunlight skittering over the rolling breakers. But there was a cold wind driving the tide in. Tiny granules of sand pecked at his face as he made his way through the dunes that fronted on to the beach.

According to the account Caldwell had given the police back in June 1977, he and his two companions had brought some bottles of beer and wine down to the beach after leaving the Victory Inn, up above the village. They’d sat in the shelter of the dunes, drinking and smoking, as darkness fell. Caldwell had fallen asleep. The deepening chill had woken him some time after midnight. He was alone, his companions gone.

Eventually, he’d travelled back to Exeter by bus and train, although the presence of Peter’s camper van in the car park had left him baffled as to what he and Alison were doing. He’d hammered on the door but got no response. Were they playing some kind of bizarre trick on him?

When they hadn’t shown up or phoned by the following morning, he and the other residents of 18 Barnfield Hill had agreed the time had come to raise the alarm, little knowing Alison Parker’s body had already been found on the beach where Caldwell had last seen her.

Nick cut back up the beach to the footbridge across the stream that ran through Porthtowan to the sea, then climbed the long slope to the clifftops south-west of the village. With the tide coming in, there wasn’t much to be seen of the shore below the cliffs, or of any of the caves into which Peter Ellery’s body might have been washed and somehow become trapped. There was no sign either of the pipe that had fed effluent from the nerve gas factory out to sea. According to one of Holgate’s clippings, there were claims by bathers to have suffered mysterious neurological complaints after swimming in the area of the pipe when the factory was active, and long after as well.

The factory had vanished many years ago, of course, along with numerous outbuildings. The photographs Holgate had shown Nick revealed what amounted to a small industrial estate on the site in the 1950s and 60s. All he could see in the distance now was a couple of low structures and a radar dome.