‘My name is Amelia Dropmore and this is my sister, Dorothy. She is eighty-seven years old, and I am ninety-two. Don’t mind her, she’s living a second childhood. The diagnosis was Alzheimer’s. She has been what they describe as “demented”, charming word, for twelve years. It’s a mercy for her, in a way, because she has no idea what’s going on. Her mind is stuck in the past. She thinks it’s the nineteen thirties and she’s a little girl and there is no sickness …

‘I am not demented. Before the sickness came Dorothy had been living here for eight years. I was still independent, but I knew the place well. I visited her whenever I was able. Like everyone else I’d thought that was it. The world would carry on as normal, Dorothy and I would grow older, and pretty soon one of us would pass on, and then the other. Nothing to write home about. Just a slow dying of the light.

‘And then it happened. Our world did not carry on as normal. It was thrown off its axis. Altered beyond recognition. At first the staff here were really very good. They did what they could for the old folks. But one by one they either took sick, or simply stopped coming in in the mornings. Who can blame them? They all had loved ones. Families to be with. So in the end it was left to me to look after the ladies and gentlemen who live here.’

‘Why aren’t any of you sick?’ asked Lewis.

‘She don’t know, do she?’ said Kyle. ‘How could she know? She ain’t no scientist.’

‘I’m afraid you are quite wrong,’ said Amelia patiently. ‘I am a scientist.’

‘You’re joking me.’

‘What? You don’t think a woman can be a scientist? Or you don’t think an old person can be a scientist?’

‘For real? You’re a scientist?’

‘Yes. I trained at Cambridge before the war, in the Department of Experimental Medicine. And when war broke out I went to work for the government at the Medical Research Council in Mount Vernon in Hampstead. Churchill was terrified that the Germans might use chemical or biological weapons –’

‘I knew it.’ Kyle slapped the arm of his chair, sending up a tiny cloud of dust that hung in the air.

‘You knew what?’ asked Amelia.

‘That’s where the disease came from, innit? It was a weapon that got out, that went wrong.’