Finally, he muttered, ‘When I was down in Devon, I read this book.’ His forefinger was tapping out a gentle rhythm against a photo of his daughter, Leanne. Even from where I was, at the edge of the bed, I could see her face, her smile, a teenage girl frozen for ever in time. His finger eventually stopped next to her face, as if he were trying to scratch his way into the shot and touch her. ‘Anyway, this book, it was written by this scientist – he was trying to explain physics and quantum particles and how the universe works, all that shit. He wrote it for morons like me, who’ll never have a hope in hell of ever understanding these things properly, but it was still a bit of a headfuck. I managed to follow some of it, managed to get confused by most of it, but there was this one thing that really stuck with me.’ He paused, fanning out the photos slightly. I could see he had five in total. The one of Leanne, one each of his sons, Ciaran and Liam, one of the three of them together, and then one of the Healy family as it had once existed: the three kids, Healy and his ex-wife, Gemma. He glanced at me and then back down at the pictures. ‘This one chapter, it was all about how quantum mechanics describes the world in terms of probabilities, not definite outcomes. I mean, I left school with half an education, maybe not even that much, so I only really get the basics, but the mathematics of a theory like that means that all possible outcomes of one particular situation – one choice – can occur. In other words, in this outcome right here, we went across the road and got Burger King tonight; but in another, we didn’t get Burger King, we got a sandwich; in yet another, we only bought ourselves coffee.’

‘You’re talking about parallel universes.’

He nodded. It was obvious where this was going now.