Scorpia

clever. The polymer and poison mix is contained in the gold. It’s sitting inside the heart and it’s not doing anyone any harm. If you leave it alone, it’ll just pass out of the system in a little while and nobody will be any the wiser.
    “But Scorpia can break up the gold. And they can do it, like Alex said, by remote control. Have you ever put an egg in a microwave? After a few moments, it explodes. It’s exactly the same here. It could be microwave technology that they’re planning to use.” Stephenson shook her head, her long hair swaying. “No. Microwaves would be too low frequency. I’m sorry. I’m not really an expert on plasmon resonance.” She hesitated. “A terahertz beam might be the answer.”
    “I’m sorry, Dr Stephenson,” the foreign secretary said, “but you’re losing me. What are terahertz beams?”
    “They’re not much used yet. They sit between the infrared and the microwave bands of the electromagnetic spectrum and they’re being developed for medical imaging and satellite communications.”
    “So you’re saying that Scorpia could send out a signal using a satellite and it would break up the gold, releasing the poison…”
    “Yes, sir. Except they wouldn’t actually need to use a satellite. In fact, they couldn’t. The beams wouldn’t be strong enough. If you ask me, when those poor men got off the plane at Heathrow, there must have been some sort of satellite dish erected. It was probably put there a long time ago, on one of the buildings or perhaps up a mast, and they’ll have taken it down by now. But all they had to do was throw a switch, the terahertz beams would have broken down the gold and … well, you know the result.”
    “Is there any chance that the nanoshells could be broken up accidentally?” Sir Graham Adair asked.
    “No. That’s what’s so brilliant about the whole thing. You’d need to know the exact thickness of the gold. That tells you what frequency to use. It’s just like when you shatter a glass by singing the right note. If you ask me, Alex saw that same technology at work with that tiger. The animal must have had some sort of sedative in its bloodstream. They just had to press a button and it fell asleep.”
    “So if they’re not using a satellite, what are we looking for?”

    “A saucer. It would look much the same as a satellite TV dish, only bigger. They’ve said they’re targeting London kids, so it will have to be somewhere in London. Probably mounted on the side of an office building.
    They may call it Invisible Sword, but I’d say it’s more like invisible arrows being fired out of satellite dishes.
    They shoot out in a straight line.”
    “And how long will it take for the gold to break up once the switch is thrown?”
    “A few minutes. Maybe less. Once the gold breaks, the children will die.”
    Dr Stephenson backed away from the table and sat down again. She had nothing more to say. Immediately everyone began to speak at once. Alex noticed some of the civil servants talking into mobile phones. The two women in black and white were typing furiously, trying to keep up with the babble of conversation. Meanwhile, the permanent secretary had leant across Alex, talking quickly and quietly to Alan Blunt. Alex saw the spy chief nod. Then the prime minister held up a hand for silence.
    It took a few moments for the clamour to die down.
    The prime minister glanced at his director of communications, who was looking down, biting his nails.
    Everyone was waiting for him to speak.
    “All right,” Kellner said. “We know what we’re up against. We know about Invisible Sword. The question is—
    what are we going to do?”

Chapter 16: DECISION TIME

    You have to evacuate London.”
    It was Sir Graham Adair who made the suggestion. This was the result of his swift conversation with Alan Blunt. His voice was soft and measured, but Alex could sense the tension. The permanent secretary was as brittle as ice.
    “Scorpia has planned this at exactly the right moment. Four o’clock. Thousands of children will be out of school—on their way home. We have no way of knowing how far these terahertz beams can reach. There may be several dishes, mounted on buildings throughout the capital … near schools, near tube stations. No child in London will be safe. But as Dr Stephenson has just told us, provided they don’t come into contact with the beams, the poison will pass out of their systems eventually. We can keep them out of the city