"But we can test the water coming in," Paine said, "and not allow it into the base supply until we're satisfied that it's all right."

"Or," Cardenas suggested, "we could run the incoming water through a nanomachine screen, program the nanos to pass only water molecules and divert everything else."

"That would help," Doug said.

"They won't be that subtle," Gordette said, still standing by the couch. "They won't want to wait weeks or months for a biological agent to take effect. Besides, they know we've got nanomachines that we could use to cure any disease they cause."

"So it'll be a direct attack."

That's what I think," Gordette replied. "They'll land their troops, bomb out our electrical power equipment, and then march in here."

Cardenas slumped in her chair. "Nanomachines aren't going to be much help, then."

"We can knock out a nuclear warhead," Paine insisted.

"Maybe," said Doug.

"How'll we deal with a whole regiment of Peacekeeper troops?" Anson asked glumly.

"We'll have to think of something," said Doug, trying to show a cheerfulness he did not feel.

"If we can keep on generating electricity…"

Doug pushed his chair back from the table. "I want to talk to the head honcho of the physicists about this particle beam idea."

"The new guy," Anson said. "He came up here on the last flight before this mess started."

"What's his name," Doug asked, "Wickens?"

"Wicksen," Paine corrected. "Robert T. Wicksen."

DAY SEVENTEEN

After the meeting Doug went straight to the office of Robert T. Wicksen. The physicist was a small, slight man, built like a sparrow, but with large, intelligent, gray eyes magnified by old-fashioned rimless glasses.

"Focus the particle beam on an incoming missile warhead?" Wicksen asked. His voice was flat and calm. He was not perturbed by Doug's question, he merely repeated it to be certain he understood what Doug was asking. Physically he reminded Doug of a tarsier: little, cautious, big staring eyes. Yet he seemed composed, unruffled, perhaps unflappable.

Wicksen's office was a cubbyhole crammed with electronic gear. No desk, not even any chairs; only a pair of stools that looked as if Wicksen had crafted them himself out of lunar metals. Yet everything was as neat as a picture out of a sales catalogue. Everything in its proper place. All the equipment humming reassuringly. All the screens displayed data curves that flickered and shifted as they spoke. Wicksen himself was equally neat, in a crisp open-necked white shirt and perfectly creased dark gray trousers.

"We need to know if it's possible to convert your particle accelerator into a beam weapon," Doug said, sitting on one of the room's two stools.

Sitting on the other stool, facing Doug like an elfish wizard in modern clothes, Wicksen nodded somberly. "It's possible. Anything is possible."

"But can you do it, Dr Wicksen?"

"Wix."

"Excuse me?"

"Wix. Everyone calls me Wix."

"All right… Wix. Can you do it?"