On Earth, two dozen global positioning satellites are enough to provide pinpoint locating fixes for virtually any spot on the globe. The satellites' orbits are fixed in space while the Earth spins below them. No matter where on Earth you are, there are always at least two satellites above your horizon to give you a precise navigational fix.

To get the same kind of coverage on the Moon, with its slow rotation rate, takes many more satellites. The consortium of private companies and government agencies that had cooperatively set up the lunar GPS system had tried to strike a careful balance between practicality and cost. They had started with a network of six positioning satellites and were adding to the web from time to time.

Just my luck to be out here at a time when the two closest satellites are both too low on the horizon for my suit radio to pick up their signals, Paul grumbled. Maybe it isn't luck. Maybe Greg timed it all. Is the kid that smart?

What difference does it make? he asked himself as he plodded across the barren lunar plain. Every few minutes he stopped to turn and see if his path remained straight, but he knew that was only the roughest of guides. You could be drifting off to one side or the other and never know it.

He sucked up a mouthful of water, sloshed it around his teeth and then swallowed it: "Hell," he muttered, "for all you know you're heading for the pissin' south pole by now."

One of the GPS signals oughtta come through pretty soon. I'll straighten out my course then. In the meanwhile, keep: pushing ahead.

In the back of his mind Paul knew, as every astronaut knew that what killed people on the Moon was fatigue. More than equipment failure or ignorance or even bad judgment, simple fatigue could wear you down to the point where you forgot just one little, vital thing. And then you were dead.

Paul forgot about the dust.

That powdery, fine dust, like beach sand underfoot, was electrically charged by the constant infall of ionized particles from the solar wind. No matter how carefully you stepped, your boots stirred up little clouds of dust, and some of the stuff inevitably clung electrostatically to your suit.

Through hard experience the men and women who worked on the Moon had learned to include a hand vacuum cleaner in the airlocks of their buried shelters. After an hour or so out on the surface, the suit needed a thorough cleaning. Otherwise the dust would get into everything inside the shelter itself.

It was more than an annoyance. Gritty dust particles worked their way into the hinges of space suits. If enough dust clogged the knees or other joints the suit would stiffen up just like the Tin Woodsman of Oz, left out in the rain. The experienced astronaut listened carefully for grating noises in his suit; kept sensitive to whether or not the joints of his suit were moving smoothly.

When they weren't too tired to remember.

Paul plodded along. He knew that he had been down on all fours back at the glass-smooth crater that he had slid into. He knew, if he had thought about it consciously, that his gloves probably had a thin sheen of lunar dust clinging to them electrostatically.

But he was too tired to be wary of the dust.

Wish I had a headband, he said to himself as he tried to blink the sweat out of his eyes. He didn't want to look at the thermometer on his forearm panel, didn't want to know how hot it really was. The Sun was broiling him, he knew that and it was enough.

The bleak plain stretched in every direction around him, nothing but rocks and dusty regolith and more rocks. In his helmet earphones he heard nothing but the precisely timed beep of his suit radio's plaintive call to the GPS satellites that were not there to answer. Like a Chinese water torture, Paul groused. Beep. Then wait. And then another beep. Where the fuck's the answering signal? At least one of the pissing satellites ought to be in range by now.

But he heard only his suit radio's patient, maddening call signal.

One foot in front of the other, Paul told himself as he pushed along. Just keep putting one foot in front of the other and you'll get there sooner or later.

His vision blurred and without thinking he wiped at his helmet visor. A film of gray smeared across the visor.

Oh crap! Just what I need; Paul grumbled to himself. The upper half of the visor was covered with dust. He had to peer through the lower half to see where he was going.

Without stopping, he fumbled in the pocket on the right thigh of his suit for an electrostatic cloth. Got to be one in there, he said to himself. If they kept the suit supplies topped off. If the cloth hasn't already been saturated.

It was almost impossible to feel anything as thin as the cloth with his gloves on, but at last Paul pulled a bright green square from the pocket. He held it up in front of his visor and inspected it as best as he could through the smear of dust. Looks good enough. Most of it was still bright green, although one corner of the cloth had turned gray. It had been used before.

Carefully folding the cloth so that the gray, used section was out of the way, Paul wiped slowly at his visor. It seemed to help, but only a little.

Ought to have windshield wipers on the damned helmets, he thought. The cloth was not doing the job it should have done. Must've lost some of its electrostatic charge while it was sitting in the pocket. It's been used before, too. Christ, it's just not working!

The gray smear seemed a bit thinner now, not as opaque. Paul could see through it as if it were a frosted window: blurry shapes and shadows, not much more.

He refolded the cloth and tried again. No improvement. All he managed to do was to smear the dust a little further across his visor.

In disgust he tossed the cloth away. It soared like a rigid sheet of thin metal in the airlessness of the Moon, spinning lazily until it sailed out of his range of vision.

"Okay," Paul muttered. "Now we play pissin' blind man's bluff all the way to the next tempo."

Then he heard a sudden chatter of beeps in his earphones: the signal from a GPS satellite. I'll play it by ear," he said aloud, and began to laugh wildly at his pun.

But he needed to look at the displays on his forearm panel to make sense of the GPS navigational signal. His laughter died as he squinted through the dust filming his visor. If he was reading the instruments correctly, he had drifted more than six miles off his course to the next underground shelter.

SAN JOSE.

The manager of the nanotech division was barely out of her thirties, young and intense and obviously nervous. Yet she seemed to be the oldest person that Paul could see anywhere in the plant. Her skirted suit of charcoal gray looked as if she hadn't worn it since her first job interview. She looked uncomfortable in it, as if she longed to be in a t-shirt and jeans, as almost everyone else was.

Paul felt like an old and stuffy grandfather in his light whipcord slacks and tan sports jacket. Good thing I didn't wear a tie, he said to himself. These kids'd think I came from Mars.

"Mr. Masterson was here last week, y'know," the manager was saying, "and he said he was very satisfied with the progress we've made in the past six months."

So that's it, Paul realized as they looked through the thick window into a clean room where white-smocked technicians were bent over laboratory benches. Paul saw that the techs wore white caps over their heads and even had white booties over their shoes. Or sandals, he thought, glancing at the manager's bare unpainted toes.

"Look," he said to her, "I'm not here to swing a hatchet, you know."

The manager's expression clearly said she didn't believe Paul. The ID badge pinned to her jacket said Kris Cardenas. She didn't look Hispanic, though. To Paul she looked like a California surfer chick: an attractive kid with softly curled sandy hair, a swimmer's broad shoulders, wide sincere cornflower blue eyes and a deep tan. And enough brains in her head to rise to the top of this very competitive high-tech division.

Making a smile for her, Paul explained, "You've probably heard that Greg Masterson and I are enemies, haven't you?"

She nodded warily.

"Well, even if we are that doesn't mean I want to kill this division just because he's backing it. From what I can see, you're doing a good job here."

Cardenas seemed to be holding her breath, waiting for the other shoe to drop.

"What I'd like to know," Paul went on, "is whether or not you're at a stage of development where we can try some practical tests of nanotechnology."

"We were ready to try clinical tests of tumor killers," Cardenas said, "but the government ruled that anything intended to go inside human patients has to go through the FDA's approval procedure, and that takes years'

"I know," Paul said. Washington's decision had sent the entire nanotechnology industry into a tailspin. It wiped out any hope of profitability for this division for years to come.

"I can show you the animal tests we've done," Cardenas said, starting down the corridor. "We can destroy tumors with better than eighty percent efficiency-and no collateral damage to healthy tissue, y'know."

Following her, Paul said, "In animals."

She nodded vigorously. "Pigs, rhesus monkeys, even chimps. There's no reason why the bugs shouldn't work just as well in humans. There's just no sense to the government's restrictions!"

With a world-weary shrug, Paul said, "I agree, but they've made their decision and we've got to live with it." Or die with it, he added silently.

"It's stupid," Cardenas insisted.

"I was wondering, though, could you adapt nanotechnology to other applications?"

"Oh, sure," she said easily, pronouncing the word shirr.

They had reached a set of big double doors. Cardenas pushed one open and they stepped through into a large room filled with animal cages. The walls and floor were tiled in white. The smell of animal fur and excrement was enough to make Paul's eyes water.

"Careful," Cardenas warned. "These floor tiles get kind of slick, y'know. The handlers have to wash them down a lot."

I'll bet," said Paul.

As she led Paul past a row of cages filled with hairless lab rats, Cardenas told him, "We're already adapting what we've developed here for other applications."

One of the monkeys yipped at them and within half a second all of them were howling and shrieking. The din was overpowering, echoing off the tiled walls like shock waves pounding on Paul's ears.

Looking worried, Cardenas shouted over the noise, "Maybe we'd better go someplace quieter."

"Amen to that," Paul yelled back.

Once they were out in the corridor again, with the heavy doors muffling most of the noise, Cardenas said, "Just about every one of those monkeys had cancerous tumors. Y'know, really nasty carcinomas and stuff like that. The nanobugs found them inside their bodies and disassembled them, molecule by molecule."

"So once you finally get FDA approval this division ought to be worth a good-sized fortune," Paul said reassuringly.

"For sure."

"In the meantime, though...' Paul let the thought dangle in the air between them.

"In the meantime," she said, leading him farther down the corridor, "we're trying to spin off the medical work into toxic waste cleanup."

"You can program the bugs to eat toxic wastes?"

Cardenas nodded vigorously. "It's pretty simple, really, compared to the tumor work. They can go through a waste dump, find the molecules you want to get rid of, and take them apart. Nothing left but carbon dioxide, water, and pure elements-which you can recycle."

"Sounds good," Paul said.

"We're trying to get the state environmental agency to participate in a demonstration we ve set up."

"Not the federal EPA?"

Cardenas wrinkled'her nose. "The feds are real assholes. My strategy is to get the state environmental guys on our side and let them convince the feds."

Paul remembered the first man he had worked for, when he had started at Masterson Aerospace. "Make the customer a party to the crime," he had advised. "Get them on your side and they'll do half your work for you." His respect for Cardenas went up a notch.

She stopped at a locked door with a RESTRICTED ACCESS sign over it. "At least this area will be quieter than the animal pens."

A few taps at the electronic lock and the door swung open. Paul followed her into a small, stuffy, windowless room crammed with consoles and instrumentation. The only lights came from the display screens on the consoles. The room felt overly warm, uncomfortably so.

As Paul peeled off his jacket, Cardenas leaned over one of the keyboards and typed out a single command. A shutter slid back from the blank wall on Paul's right and he saw a window that looked into another room.

An ancient Cadillac sat in there, one of those old monsters heavy with chrome and tailfins. Bright red, where there was paint still on it. Almost half the side that Paul could see was dull bare metal. The car was up on blocks, although the rear tire was still on its hub. The front tire was gone. The hood was propped up part-way; the windshield wipers were gone.

"What's this?" Paul asked. "A pop art exhibit?"

Cardenas grinned at him. "It's our toxic waste exhibit. What do you think of it?"

Paul turned back to stare at the Cadillac through the thick window. "Nanobugs are taking it apart?"

She nodded happily. "We've got four different types of specialized gobblers in there."

"Gobblers?"

"Nanomachines specifically designed to attack certain molecules, break them apart into their constituent atoms."

"Gobblers," Paul repeated.

"One set's taking out the paint," Cardenas explained. "Another is reducing the organic molecules in the tires to carbon dioxide, methane, and whatnot The third is working on the engine, separating out all the tungsten and platinum in the steel alloys."

"Tungsten and platinum?"

"They're valuable metals, y'know. We want to separate them out so we can recycle them."

"I see," said Paul.

"And the fourth set of nanos is gobbling the plastics in the dashboard, steering wheel, seat covers and such."

Paul could see the sheer fervor of achievement radiating from her face. A muffled bang made him snap his attention back to the Cadillac. The one tire remaining had just blown out and now hung limply on its hub. Paul thought he could see it twitching like something alive being devoured by parasites.

"Why do you keep the car in a sealed chamber?" he asked.

"To keep the bugs from spreading, of course," Cardenas answered. "We keep the chamber at ten below zero, Celsius. The bugs are programmed to stop at any temperature above zero."

"But why-"

"To make sure they won't start gobbling people!"

"Oh." Paul hadn't thought of that Cardenas didn't seem the least bit condescending as she explained, "The bugs don't see any difference between your molecules and the Cadillac's, y'know. Except temperature. We design them to immobilize themselves 'way before they get to human body temperature."

Paul nodded slowly. "Then how do you expect to use them in toxic waste dumps if you're worried that they might attack people?"

Her smile faded slightly. "We're working on that problem. We've got to make them much more specific than they are now.

Much more specific. Tailor them to distinctive molecules, so they'll gobble those molecules and nothing else."

"Can you do that?"

"In time," she replied.

Time costs money, Paul knew. It was the old story: an exciting new possibility that could make fortunes of profit, but first you have to sink fortunes of investment into it and pray that it eventually succeeds.

"What else do you have?" he asked.

Cardenas went back to the control console, flicked her fingers across a different keyboard. Another section of shutters slid back, this time on Pauls left.