The guard had gone. Sanders looked towards Hepton and shook his head: there was no sign of Villiers. Hepton couldn’t help wondering how hard the guards had tried. He also wasn’t entirely sure that he could trust Sanders himself. Yet here he was, having the conversation he wanted with the people he needed to speak with. He took another breath, his heartbeat slowing a little, the roaring in his ears more of a gentle breeze now.

‘The day the shuttle crashed—’ he began. But Parfit interrupted.

‘Wait one moment, would you, Mr Hepton? I’m going to put you on our conference facility, so that Major Dreyfuss can participate.’

Hepton waited impatiently.

‘Okay, go ahead now.’

He began again. ‘The day the shuttle crashed, about the time Argos was launching a satellite or whatever it was doing up there, our satellite went haywire. A friend of mine had an idea what had happened, but he ended up dead. Before he died, he gave me one word. That word was Argos.’

There was silence at the other end. Hepton glanced towards Sanders, who was listening intently.

‘Martin?’ It was Dreyfuss’ voice. ‘What do you think happened?’

‘I’m not sure. But people are getting killed because of it.’

‘All right then,’ said Dreyfuss. ‘Listen, I’ve got part of a sequence. I wonder if you know what it means. The whole sequence was much longer, but all I have are the first few letters and numbers.’ He paused. ‘Ze/446.’

Hepton smiled. He could have completed the sequence for them if they wanted.

‘That’s an easy one,’ he said. ‘It’s Zephyr, of course. It’s part of Zephyr’s identification code.’ His smile vanished. ‘How did you get hold of it?’

‘One of the crew on the shuttle had it on his screen. It kept flashing up.’

Hepton’s blood went a few degrees colder. ‘Then you were trying to lock onto Zephyr.’ It was a statement.

‘That’s just what I was thinking.’

Parfit’s voice came on the line. ‘Tell me about Zephyr, Mr Hepton.’

‘What do you want to know?’

‘What exactly does it do?’

‘It’s an all-purpose satellite, as versatile as we want it to be.’

‘What was it doing the day it went haywire?’

‘Not a lot. We’d been running some regular checks on it.’

‘Well, what might it be doing now? Any specific jobs it was supposed to carry out?’

‘A few. The big one, I suppose, is monitoring the troop pull-outs.’

‘The pull-outs?’

‘Nobody’s supposed to know. But we’ve been keeping an eye on the US bases in Britain.’

‘But why?’