Kate felt two stone lighter. Somehow, the absence of one teenage monster made the whole Citadel feel less frightening. She pushed the dead clone from beneath her, and took his spot on the bloodstained mattress.

‘Wonderful news,’ answered McCormick, albeit with a humane twinge of guilt, ‘but I’m afraid he’s only bonus points. If the shield goes up, we still lose. It’s twenty past nine—’

‘Leave it to me, sir,’ Kate interrupted. ‘Go as fast as you can, but don’t do anything stupid. You’ll have more time than you think.’

She focused one eye through the sniper’s scope. Through the lens of a telescopic sight, the whole world looked different. And not just because of the occasional tremble of focus, or the blur around the scope’s edges. Through a sniper rifle, every detail on the ground looked like something to be inspected rather than seen.

She was thankful the wall faced north. The glow of the sunset was on her left, rather than in her eye. Plenty of twilight remained – twenty past nine wasn’t so dark in May – but she didn’t have long before the awkward part of dusk when it was too dark for plain sights, but too bright for night-vision.

Her search began. She knew exactly what a border point looked like, having seen them up far too close at Oakenfold. A little part of her brain, which had been suffering from enormous anxiety at the moment the memory was made, remembered that each border point had its own miniature shield. Perhaps that meant that the loss of any single coordinate would bring down the whole network.

Now, without the shields raised, the border points would not be impervious to bullets. Or at least, Kate hoped not.

She found a landmine-shaped lump of metal in the grass within the first two minutes of her search. She fired a bullet straight into it, and in the dimmed light she saw a glimmer of metal somersaulting through the evening air like a tossed pancake.

Kate smiled. It had been her first smile since the day she and Raj had watched the missiles over New London. Maybe, just for tonight, she was going to be OK.

The border point had landed the right way up, but the LED was blank. It was out of action. In ten minutes’ time, Grant would push the magic button to a fanfare in his head, and be sorely disappointed. It could take hours for that point to be located and replaced.

‘Ewan,’ she said to the radio, ‘you can scrap the time limit. I don’t know how long we’ve got, but it’s more than ten minutes now.’

‘Prove it.’

‘I just shot a border point with a good quality sniper rifle. The shield won’t activate unless every link in the chain is working. We’ve got loads of time before they replace it.’

Ewan didn’t answer, suggesting he was satisfied.