I looked at an alarm box, high up on the front of the house, and to similar ones on the other two. When we’d entered earlier, Ross had put in a code. He’d told me that he knew the codes for the other properties too.

‘When you arrived here on the 3rd of November,’ I said, ‘was the alarm set?’

‘No. None of the houses had their alarms on.’

It was hard to know whether that meant anything or not. The couples were going to a dinner party less than a minute’s walk away and the houses were in a remote location where the threat of crime was minuscule. They’d locked up their homes that night but there were almost certainly times before that when they’d popped in to visit each other and hadn’t even bothered doing that much. There were probably times when they’d gone further afield and never bothered setting the alarm either, because of how low risk the area was. I’d noted that the Perrys’ alarm – and most likely the others too, because they were all fitted by the same firm – had a police response function on it, which meant that if the alarm went off in suspicious circumstances, the security company informed the cops. But that was irrelevant if they’d never been set in the first place.

I walked over to John and Freda Davey’s home. Their house was much less contemporary, the furniture more functional, perhaps a reflection of the fifteen-year age gap between them and the Perrys. It was lovingly put together, though, photos of their kids – Rina Blake and her brother, Ian – absolutely everywhere, along with pictures of their grandchildren: Rina had a girl and a boy, although the boy wasn’t in any of the pictures here because he was only about a month old; Ian had one boy, and in most shots was in Singapore, where he’d lived and worked since 1999.