McCormick looked at Grant’s face, and used a voice that made his plea sound as gentlemanly as possible.

‘Before I die, I’d like to know what this war is truly about.’

Grant began to laugh, longer and louder than he had all evening.

‘You think we’re opponents in a war?’ he asked. ‘You’re nothing more than civil unrest! An unwelcome brawl! A minor inconvenience from dead men walking! For you, it must look like the biggest war humanity has ever fought. But from my perspective—’

‘Answer my question. Now, please.’

Grant smiled, almost entertained by McCormick’s attempt at a command.

‘I’m going to miss you, Joseph. May I call you Joseph? It’s a shame we’ll only ever get this one chance to talk.’

‘Then let’s make it count. Is this about world domination? Is that your master plan?’

‘World domination,’ Grant repeated with childlike laughter. ‘I dislike that phrase. I don’t want to dominate the world. I just want to subdue it.’

‘But why?’

McCormick was not expecting an answer. When Grant gave one, his heart stood still.

‘Simple. To cull the human population.’

The breath caught in McCormick’s throat, and he could not ask for details. But Grant sensed the question.

‘Nine billion people live in this world. That’s about six billion too many. Everyone goes on about wanting to “save the world”, but the world looked after itself just fine before humans came along. If it needs saving, it needs saving from us.’

McCormick found himself muted. Just when he thought nothing else could surprise him about life on the upper floors, the great Nicholas Grant – son of an oil tycoon – had revealed himself to be an eco-warrior. But not the progressive, philanthropic type, like those who had protested government inaction on climate change before Takeover Day. A rich, powerful, genocidal eco-warrior.

‘Once the power of humans has withered, it’ll give the planet some time. Rainforests will grow back. Polar ice caps will stop melting. Nature will have its oceans back. And once there are too few humans left to wreck the world again, we’ll close down the Citadels across the globe, purge the clones and allow the survivors to rebuild. But that’ll be generations from now. I don’t suppose I’ll live long enough to see the world safe again.’

‘What you’re suggesting is monstrous…’ McCormick said as he found his voice again.

‘Monstrous? Consider this, doctor. The end of every geological era – Triassic, Jurassic and so on – is marked by a mass extinction. The meteor that killed the dinosaurs was the Cretaceous–Paleogene extinction event, which killed three quarters of all animal species. The Permian–Triassic extinction event killed ninety-six per cent of everything. But those extinctions took place over thousands, maybe millions of years.’

Grant walked to within a metre of McCormick, so he could lower his face to finish his point.