She paused, and we waited for her decision. I think she found it difficult as an emotional human, but her rational, scientific brain took over.

‘Mortality must resume. People in this care home must continue to die. Not at the old rate, because that would cast doubt on the achievements of the nanobots. Typical rates of mortality in a home like this are around 26 per cent a year. We have 108 residents. If we aim for around 20 per cent, it’s a significant improvement but not so great as to arouse suspicion. Good for business, but not too good to be true.’

‘We therefore need a death every 18.25 days,’ said Robert. ‘And we have had none since March.’

‘We can’t have a catch-up flurry of deaths,’ said Dr Morton. ‘It would be too distressing for the residents and relatives, and would attract attention. No, start now, and aim for one every two to three weeks. And don’t let the nanobots terminate their hosts. In case of autopsy, we must use natural agents such as infections.’

‘We have to choose one for this week,’ said Robert.

‘How?’ asked Herbert.

‘Is anyone ill?’

‘No. We’ve cleaned up the whole bio system. Visitors and all coming from outside are screened. We’ve pre-empted everything down to asymptomatic infections.’

‘As with Cecilia Winter?’

‘Yes. The probability of another one like her is small. At least within an acceptable time frame. We’ve ring-fenced the residents as completely as possible.’

‘OK, of course we have. And we’re not changing the protocols.’

‘Very well,’ said Doris. ‘We can introduce pneumonia to one resident. It’s plausible and relatively painless. Who shall it be?’

‘I agree not Mrs Winter,’ said Robert. ‘Too interesting. Go for one in the eighties – we have plenty of them.’

‘OK. Random selection. Wait. Number fifty-six generated. Mrs Margaret Woodruff.’

‘She’s beyond expectancy,’ I said. ‘Current improvements much commented on by her family – but in the end, they expected her to die soon until recently, so they’ll revert to that and rationalise it. I’ll introduce pneumonia tonight. She’ll die within the week.’

‘Thank you, Winifred.’

Margaret

I’m in the garden again, looking at the plants in the evening sunlight. It’s miraculous. I can see, and so clearly now – I can hardly believe it. I want to see everything again, everything I lost. It’s all I want to do. Let the world enter my eyes. Look, birds are feeding on the grass, hopping about, fluttering up and down from the trees. I watch in complete peace.

Winifred comes out into the garden and sits down next to me. For a while nothing is said. Then I turn to her.

‘This is my favourite time of day to be out here.’

‘What does it make you think of?’

‘Oh… many things. My childhood. We had a big garden then. My house – my garden was my pride and joy. I shouldn’t feel pride, should I?’