At the boy’s feet were a bunch of envelopes – the ones Jack had told him to hide under McCormick’s mattress and given no second thought to ever since. A look of fright appeared on Thomas’ face as the envelopes landed face-up. The top one read ‘Mark’.

The young man stormed over, ignoring Thomas’ desperate protests, and ripped the envelope open.

‘…I promised McCormick…’

Mark brushed Thomas to the side, and started to read. Jack ran over to look.

Dear Mark, the paper began.

10:28 p.m.

Ewan checked his watch, and swore.

He and Alex had been trapped in the stairwell to Floor C since they had arrived. So near to Marshall’s computer, yet so far.

The lower door burst open, too fast for either of them to ready their weapons. Thankfully the intruder was Kate, with a golden keycard in one hand and her detonator in the other.

‘You found a human then,’ said Alex.

‘Yeah,’ said Kate. ‘…I knocked him out.’

Ewan looked at her face. It reminded him of his own face on Takeover Day, right after he realised he had made his first kill.

‘Right,’ said Alex, ‘let’s get going.’

‘No,’ said Ewan. ‘Not for another minute and a half.’

His friends glared at him as if he had personally insulted them.

‘Whatever that detonator does, I’d rather get my breath back now and take Floor C by surprise after it goes off.’

He didn’t know whether Kate and Alex agreed with his strategy, but the suggestion of catching their breath was well-received. Kate climbed to the top step and sat down in front of the door.

She was afraid. Afraid enough for the detonator to tremble in both hands as she brought it close to her face. Ewan remembered McCormick’s sadness when Kate had volunteered for the task. He had never been one to underestimate his soldiers, but he must have had his reasons.

There was only one decent thing to do. Ewan climbed to the top of the stairwell and sat down next to her.

‘Alex,’ he said, ‘sit there.’

Alex rolled his eyes, but knew there was no time to argue. He sat down on Kate’s other side as commanded. Between them, Ewan could sense Kate’s chaotic breathing through the rising and falling of her ribs.

‘Kate,’ he said, ‘flip it open.’

Kate took several seconds to do so. Partly because of anxiety, striking at the most predictable but least convenient time, and partly because it was difficult to operate her twitching fingers.

But she did so, and the metal casing sprung open to reveal a solitary, harmless-looking clear button that would change the face of the war.

Ewan stuck out a thumb and aligned it next to Kate’s. He glanced at Alex, who got the message and did the same.