The others were fitting their own shoes. Hector, Woody and Angel watched them. When they were done, Hector spoke. ‘It’s time to go. Follow me.’

They filed across the room to an exit guarded by an armed police officer. She gave the recruits a strange look as they walked past her, but said nothing. Waiting immediately outside was a white transit van, flanked by two police cars. The van’s side door was open. The recruits and the Watchers entered and sat along either side of the van. Max noticed that they automatically took the same positions that they had on Green Thunder. Someone outside slid the door shut. Police sirens started up and the transit van moved away.

‘We’ll be on site in approximately fifteen minutes,’ Hector announced. ‘When we get there, you’ll be shown a map of the school and be given a final briefing. In the meantime, I’m going to give you a crash course in communications. You’re all wearing a wire. Once the operation starts, you’ll be able to hear the control room and we’ll be able to hear what you say and anything going on around you. Your microphones are very sensitive. They’ll pick up what you say, even if you speak quietly. But you have to use your head. If the terrorists see you muttering to yourselves, they’ll soon realise that something isn’t right. That method of communication is only suitable if you’re completely certain nobody is watching you.’

‘What if somebody is watching us?’ Abby said. She sounded stressed. Max was prepared for Hector to scold her for interrupting him, but he didn’t.

‘In that case, you speak out loud, but you do it in such a way that nobody knows you’re communicating with us. That means encoding your messages in some way.’

‘What?’ Jack scoffed. ‘You want us to start talking gobbledegook over the microphone and hope that doesn’t make people suspicious?’

Hector gave him a long look. The kind of look that could silence even a kid like Jack. Then he continued.

‘The trick is to hide the message you want to transmit in normal-sounding conversation. For example, if you want to let us know that a child is hurt, say it to one of the terrorists. If they think you’re having a conversation with them, they’ll never guess that you’re relaying information to us at the same time. Is that clear?’

They all nodded.