Some of the nanobots migrated to the palm of the hand and emerged at the surface of the skin as a complicated dark red ideogram. Cheaters, parents who had tried to fill out their children's forms, or family members who had taken it upon themselves to speak for other family members, plus those who had discarded the questionnaire or simply ignored it, received on the following day a stern note and a new questionnaire. Though the questionnaires were in fact returned to a central depository, from which they subsequently disappeared, the work of tabulation had already been done. Newly assembled nanobot structures inside each person now identified that person. Roving structures migrated throughout each person's body, correcting minor physical problems as they went. Crippling diseases were ameliorated.

Incapacitating pain was relieved, but fatal diseases were let alone. No attempt was made to reduce drug addiction, alcoholism, smoking, or any other self-destructive behavior.

When anyone shook hands, hugged or kissed, took a receipt from a cashier's hand, took a ticket from a parking attendant or money from a teller, nanobots passed from one body to another. Except for a few thousand eremitic individuals, within a few days even those who had resolutely refused to fill out a questionnaire were colonized and identified. Since the opinions of the hermits could, the Pistach thought, be accurately inferred, they were not required to answer questions.

Except for the clearly visible marks on the palms of their hands, the nanobot invasion went totally unnoticed by the people of the United States.

Law enforcement-MONDAY Captain Riggles, Morningside Precinct, looked up from his desk impatiently. "What?"

"This box for you, Boss."

"What's in it, McClellan?"

"I don't know, Boss. Says it came from them."

'Them who?"

"Them, sir. You know. The ET's."

Captain Riggles smiled grimly and commented, "As I was just saying this morning to Lieutenant Walker, McClellan, I'd be really surprised if you make it through the next few weeks to retirement. Aren't you a little old for-"

Mac drew himself up, scowling. "Captain, the box says it comes from the ET's. Right there. Ex-tra- ter-rest-rial En-voys. Now if you don't want it, sir, you just say so, and I'll dump it down in the basement with the old files."

"Give it here." He frowned at the box, a sizeable one. "Maybe it's a bomb."

"No, sir. It's been through the scanner. I've slit the tape, you just need to..."

"McClellan, I know how to open a box."

He opened it, disclosing a great number of closely packed smaller boxes, one of which, on being upended and shaken, dropped a wrist-watch on his desk. Something that looked like a wristwatch, at any rate.

"What th . . ." He picked it up and turned it in his hands. An expansion band. A round dial. A single hand, pointing down. Left-hand side of the dial green, no numbers. Right-hand side red, numbered from the top down, one to ten. Legibly lettered on the left, the words, "No probable cause." On the right, "Probable cause."

"There's directions, Boss."

McClellan handed him the thin booklet that had been wedged between the smaller boxes and the carton.

Introducing the Causometer, for use by police, drug enforcement officers and the U.S. Customs.

Provided with our best wishes by the Extraterrestrial Envoys.

"The instruments in the carton you have just received are units in a new system designed by the ET's to provide you with better tools for your work. All illicit drugs entering the U.S. will henceforth emit a harmless form of radiation which can be picked up by the devices you are now examining. To turn on the device, simply press the button on the right side. A small light will flash at the bottom of the dial indicating your position. The dial is the area in front of you. If there are illicit drugs in the area, the light will split into two, white and red, and the red light will move in the direction of the drugs. At the same time, the hand will move through the green zone toward the red zone.

"As you move in the direction indicated by red light, the two lights will come closer together. When the two lights converge, this indicates you are standing upon or at the drugs in question. Touch the device for three seconds to whatever person, container, vehicle or surface is nearest. If there are several persons or things, touch each in turn. If the thing or person touched is or has been carrying drugs, the hand will move into the red zone of Probable Cause. When the hand reaches Probable Cause, the causometer also records and emits data regarding the time, the geographical and physical location, the identities of all persons in the immediate vicinity as well as the type and quantity of drug present. This information is then sent to you in official form.

"Though the radiation is harmless, it does accumulate in persons, vehicles, or buildings repeatedly exposed to the manufacture, storage, transport, or sale of illicit drugs. The higher the reading, the more involvement there has been. A reading of four or higher indicates consistent and continuous presence of illicit material. If drugs have been dropped or deposited in a noncontiguous location, press the button on the left side, then apply the meter to the drugs first, and then to persons one at a time. DNA traces on the drugs or their packaging will be matched to the person who carried or processed them. The meter will sound an audible alarm when the right person is identified."

McClellan had been reading over his shoulder. "They're kidding."

"Somebody's idea of a joke," the captain muttered, tapping the gadget on his desktop. "Just for the hell of it, let's try it. Go down to the evidence locker and bring up some stuff. Any stuff. Hide it out there and yell."

"You mean, now?"

"No, McClellan. Next Tuesday. Of course I mean now!"

Fifteen minutes later, responding to McClellan's hail, the captain, device on his wrist, eased out of his office observed by a sniggering clutch of on and off duty cops. He pushed the right button, blinked for a moment, moved to his left, touched a desk. The needle went to red three, moving to four as he opened a drawer and took out a plastic packet with an evidence tag on it. The light had begun blinking again. He went left, right, straight ahead, uncovering five more packets of varying substances. The audience of cops, who had stopped sniggering when the first package was found, mostly had their mouths open.

"It's like a sniffer dog on your arm," said one.

"You got 'em all, Boss," said McClellan.

"No, there's more," said the captain, still moving, bumping into an off duty cop who was standing in the door. "Sorry, Stevens." He went around him, stopped, turned around, came back, reached out and touched Stevens with the device. The needle hit the five.

"Hey, what's this," Stevens blurted, turning brick red.

The captain stared at the dial which was giving him an unequivocal "Probable Cause." "Search him,"

he said to McClellan. "Now."

"Oh, come on, Captain," Stevens cried.

"Do it, damn it."

They found the packet of cocaine stuffed under his belt, in back, where Stevens had put it when he came off duty at the evidence locker. He hadn't even taken the trouble to remove the evidence tag. While they were still standing around, muttering about it, the clerk brought a fax that had just printed out.

Headed with an official-looking letterhead, it gave the date, time, location, amount and type of drugs in each discovery, place found or person in possession, list of all other persons present, and a cryptic signature.

When Stevens had been taken below and locked up, the captain brought out the carton of wrist sniffers. "McClellan, you and Brown distribute these things to the men, see the other shifts get them too.

Run off copies of these two pages that tell how it works. When the day shift gets it figured out, send two cars over to the Morningside Project. No, make it four cars and a wagon. Don't bring in any kids under ten. I got a feeling we'll make a clean sweep."

The ET's had misled the captain, though only a little. The radiation emitted by illicit drugs was high- frequency sound, a supersonic howl coming from assemblies of nanobots that had been sown some time ago throughout the coca plantations and poppy fields of the world. Nanobots, Chiddy and Vess had agreed, made more sense than any other form of tracer, because they were self-perpetuating. Designed to utilize only molecular assemblies found in drugs for replication materials, they settled in and procreated like bacteria, making millions of themselves virtually overnight. Whenever an area became overcrowded, millions migrated away to other plants or trees, carrying the useful assemblies with them. Within a period of days, there was no source of either cocaine or opiates anywhere in the world that was not fully tagged.

The nanobots had been designed to be impervious to refining processes. They didn't show up on scanners. They didn't show up on anything manmade except electron microscopes, and even then, only if someone knew what to look for. Their supersonic howls were detectable by the wrist sniffers, of course, but wrist sniffers could not be taken apart for examination. Any attempt to do so resulted in a foul stench and a puddle of unpleasant and rapidly evaporating goop.

The drug-bots were designed to penetrate wrappings, they were programmed to move out of the drugs into the clothing of the carrier, into the hair and body of the carrier, into the vehicles the carrier used, into the money the carrier received. If there were no drugs in the environment, they could not replicate, and their life spans were designed to be short, thus eliminating the possibility of innocent persons being identified as carriers. They were designed to take particular actions in response to specific signals. With a wary eye on the economics of the situation, neither Vess nor Chiddy had ordered them to do anything else, yet.

Incident in Virginia-MONDAY Late Monday evening, an armored truck made its way down a lonely country road in Virginia, headed toward an abandoned farm that was owned, ostensibly, by a widow in Baltimore. The woods behind the house were cut by the arcs of three concentric fences, an outside, slightly saggy one of rusty barbed wire, a second one of tight electrified mesh, and a third, the one nearest the house, of high-tension cables and electrified chain link with concertina wire at the top. This latter barrier, invisible from the road, began at a ramshackle shed connected to one side of the farmhouse, circled into the forest, and came out at a dilapidated annex at the other side. The splintery boards and flaking paint off the farmhouse hid a reinforced concrete bunker at the entry to a large storage area buried in the hillside. What one saw from the approach was an assemblage of rotting rail fences outlining weedy fields that ran up the slope to the house, its sagging roof part and parcel of the whole, sorry picture.

Dink was driving, with McVane beside him. Briess, a small man with a ratty mustache, was standing in the tall, armor-plated body of the truck. Arthur was on urgent business elsewhere, but his place had been taken by a sound technician and half a ton of equipment designed to detect every physical manifestation that might occur when they arrived at the ramshackle house.

"We stay in the truck, right?" Dink asked, as he came to the last turn in the driveway.

"We stay in the truck," agreed McVane. "If these creatures are what we think they are, they've had appetizers in Oregon and an entree in Florida, and I'm not offering to be dessert."

"What's your guess?" asked Dink, braking the van to a halt and shutting off engine and lights. "About what they want?"

"They're obviously a competing group," said McVane. "A rival clan, or nation, or political party. A rival world, or association of worlds. The voice that spoke to me said the Pistach aren't the only ones.

This implies we're being given a choice between the way the Pistach are shoving us and something else.

They want to make a deal."

"For what?" breathed Briess from the hatch leading into the truck body. "Hunting rights?"

"Something like that," admitted McVane. "We could tolerate that. Hell, China's got enough surplus people to keep 'em busy for a few thousand years. If their offer's good enough."

"You don't know how many of them there are," said Briess, through a grilled hatch behind the seat.

"Or how much and how often they eat. You don't know if they have a preference in taste. Like Europeans, or Americans."

"I doubt we taste any different," grunted McVane. "If they preferred light meat, they'd be talking to somebody besides us."

"How long until?" asked Briess.

McVane consulted the illuminated dial of his watch. "Ten minutes. I didn't allow much extra time.

It's boring to sit around waiting for stuff to happen."

"Crack that window so we can hear," said Dink. "Get a little fresh air in here."

"Keep it closed," barked McVane. "Turn on the recirculating air conditioner if you have to, but keep everything closed. Physically, we're probably no match for these creatures, and it's remotely possible this is a trap . . ."

"I thought you said it would be perfectly safe!" erupted Dink.

"I said a trap was remotely possible, Dinklemier. Calm down. If you want to listen, turn on the exterior mikes."

The mikes were turned on to admit a soothing murmur of light wind, the rustling of dried leaves, the flap-flap of a strap of harness hanging on the fence, the flutter of a tattered white towel that was inexplicably clipped to the washline beside the house.

"What's that doing there?" asked McVane, nodding at the towel. "I thought the place was abandoned."

"It's meant to look abandoned," Briess corrected him. "The towel means there was nothing dangerous here when the crew looked the place over shortly after sunset. The whole area has been under surveillance from across the valley since then."

They sat. "Did you locate the intermediary's kids?" McVane asked.

Dink grunted. "They're being watched. We can pick them up any time. The same with the husband.

We can pick him up any time. He doesn't know where his wife is."

"Neither do the children," said Briess. "But the boy is willing to try and find out. Seems he's got a girlfriend who likes money."

"Don't they all," murmured McVane. The rustling and flapping went on as the minutes passed, ten, twelve, fifteen.

"They're late," said McVane.

"On the contrary," said a voice through the speaker. "We arrived here when you did."

Those in the truck straightened up and peered in all directions. There was nothing visible.

"Show yourselves," said McVane.

"Rather not," said the voice in a toneless, mechanical voice. "Rather just do our business, get on with our lives, you know. Too much formality stifles us, doesn't it you? Warriors and hunters don't need it."

"You are a ... warrior race," said Briess, through the inside microphone.

"Oh, indeed."

"You speak English?"

"We're speaking through a translator. We buy them from the Pistach. Good manufacturers, the Pistach. Stodgy as all get-out, everything just so, but perfectionists do make good merchandise."

"They say they're here to help us," offered McVane. "Isn't that true?"

"Well, help is as help is. If you do it their way, you'll learn to get rid of some of what they call your native barbarism, you'll become more civilized, which is also what they call it, and you'll keep everybody reasonably happy by eliminating a lot of what makes life interesting. Maybe that's help. For us, it'd be deadly dull. We're highly selfish and individualistic. We revel in the unexpected. We lust after the hunt.

We've given you a looking-over. We think you're more like us than you are like them."

"And?" breathed Briess.

"Our view is that those who sign up for somebody's free course in social engineering ought to have a choice. If you sign up with us, we make a deal. We get to hunt on this planet. We'll set a game limit that won't overstress the population, though right at first you'll need a hell of a lot of weeding out. We can use our young ones for that. You know kids. Always hungry."

"And what do we get out of it?" Briess asked, surprised at the dryness of his throat.

"You get your population problem solved without having to argue about sex or religion or human rights. Let people have as many offspring as they want, the young ones are juicier anyhow. We prefer to maintain a large gene pool by eating only third birth order or higher persons, so we won't be reducing you by much."

"We can handle our own population problems," growled Briess.

"Never in a million years," said the voice, the translator managing to imply a chuckle. "Not with all your taboos. Aren't you sick of them? By Charm the Great, between your religions and your laws, you can't have a good gang rape without being hauled up short! That's what you get with a differentiated society like the Pistach. Everything smoothed out, ironed over. Well, with us, it's different. You let us hunt, we'll do you favors, give you some technology that'll advance you a few centuries."

"You'll restrict your hunting by agreement?" asked Briess. "How would that work?"

"First, you can tell us where the hunting should be done. Second, you can tell us what individuals or groups you'd like eliminated. Political foes, maybe? Certain foreign elements? Certain dictators that've been hard to handle? Just imagine, you want it, it happens, but nobody can trace it back to you!"

"If we make a deal with you, do we still get to join this Confederation the Pistach keep talking about?" asked Dink.

"Go ahead and join, just don't tell the Pistach about our agreement. You can go ahead and become neighborly. It won't hurt you. But ... on the side, when you get bored, we'll take you hunting with us."

There was a long silence. Briess asked, "Won't the Pistach find out about it?"

The voice made a grating noise they interpreted as laughter.

"With all your terrorists and warfare and tribal conflicts. Not so they can prove it."

Briess said, "We'd like to talk about this, a bit."

"Take your time," said a voice. "Take all the time you need. Meantime, just to illustrate our goodwill, give us a few names. We'll find the being or beings, wherever it is or they are, and we'll either make them disappear or deliver them to you. Just to show how useful we can be."

Silence in the van. It was McVane who spoke at last. "A woman named Benita Alvarez. The intermediary for the Pistach envoys."