“I know.” Herb was becoming quite angry. “I also know that you use them with caution. You don’t want them getting away and converting everything around. And that you have to tailor them to the prevailing conditions. Those set to find and reclaim silicon would be no good in water.”

Robert ignored him. He waved a hand at the VNM he had taken from Herb’s accidentally destroyed planet.

“This machine that you built does its own conversion. Its silvery color is due to the prevailing mineral content of the area of the planet where it was released. If someone were to travel over your converted planet, I imagine the color of the machines and makeup of the machines they saw would vary according to the former local geology.”

“That’s right. I know. I designed it.”

Robert looked a little surprised.

“Surely you mean, you purchased the design for a type six self-replicating machine and made the appropriate modifications?”

Realization flashed through Herb. It finally hit him. He finally understood.

“You’re doing this deliberately, aren’t you? Every time things get tense. You do your best to get me annoyed, just to take my mind off things.”

Johnston smiled. “That’s right, Herb.”

The smile widened. Herb counted ten teeth, gleaming against the pink flesh behind Robert Johnston’s dark lips.

“I didn’t want you concentrating too hard on the fact that we were about to descend onto an Enemy planet to steal some of its building blocks for our ship, or that this region of space has been seeded with security nanotechs, several of which have attached themselves to our ship and are currently at work converting our hull into more security nanotechs. I’d guess we have about ten minutes before this lounge dissolves before our eyes.”

“Don’t they think we’re on their side like everything else in here?”

“No. Too small. They’re not part of the security web. They’re just here as another line of defense in case the web doesn’t work. It’s a very effective passive defense, too: they’ll eat anything that isn’t labeled as inedible.”

“Well, label us inedible.”

“I’m doing that even as we speak. They’re transmitting a code using a public key system. Obviously they inherit the key from each other when they replicate. If I can figure out the key and send back a message encoded using the private key, they should trust us.” He closed his eyes.

“Come on,” said Herb, squirming nervously on the sofa. “They’ll be through any minute now.”

Robert opened his eyes in puzzlement.

“Oh, sorry. I solved that problem while I was explaining it to you.” He tapped his head and rolled his eyes. “I must remember to keep you informed. No. I was just working out the coordinates for the transition to the planet’s surface. Okay. We’re jumping now.”

Herb clenched his left fist in frustration. His right hand was too sore from clutching Robert’s machine.

“What is the point of me being here?” he complained. “I can’t think fast enough to beat the Enemy. I don’t know what to do, anyway.”

“I need you to press the button that makes that VNM reproduce, remember?” Johnston replied, pointing to Herb’s right hand.

Herb looked at him in disbelief. “Is that it? Couldn’t you place it on a timer or something?”

Johnston shook his head slowly and sighed. “Oh, Herb. Why won’t you trust me? There are some aspects to this mission that only a human can accomplish. If you will just be patient, you’ll see what they are. Okay. Let’s jump.”

There was a sudden discontinuity and then they were hovering above the surface of the destination planet.

“Nighttime,” said Herb.

“No,” muttered Robert, distantly. “We’re in interstellar space. This planet has no star. It wanders alone.” He nodded thoughtfully. “There are more of these planets than you might expect; they’re just incredibly difficult to find. Hold it. I’ll adjust the view so you can see better.”

Virtual daylight filled the ship as he adjusted the viewing field’s output, pushing everything into the visible spectrum. The ship was floating over a silver sea studded with rocky columns and promontories that trailed away from a row of cliffs. Everything had a spongy, desiccated look.

“They’ve gone for the metals first,” Robert murmured. “The sea below is a nickel iron alloy. This planet must have been mostly metal. Come on, let’s feed the ship.”

They began to descend, the metallic sea appearing to expand as they sank toward it.

“How long does it take this ship to absorb matter?” Robert asked. He glanced up and backward at a viewing field located just behind his right shoulder.

“It depends,” answered Herb. “Usually it takes it on board and plates it in a layer just inside the hull. It’s gradually transported from there to the necessary locations as part of the ongoing maintenance and repair procedure.”

Johnston nodded. “I guessed as much. And how long to take the necessary material on board?”

“A couple of minutes, if that.”

“Good. We’ve got just about enough time, then.”

“Just about enough time for what?” Herb asked. Something about the way Robert spoke brought the never too distant feeling of fear in his stomach back to the fore.

The robot did something to one of the fields. The view focused on something, pulled back and refocused, pulled back again and refocused once more.

“Just enough time to get away from that,” he murmured.

Herb gazed at the viewing field in horror. From the high vantage point of the virtual camera he could finally make out what was going on. The sea over which they floated was crystallizing in a circle around them. It was as if a rime of white frost was settling on the surface of the gently moving liquid metal and freezing it into a rapidly tightening noose of ice. Herb could see their ship, clearly marked as occupying the center position. The bullseye.

He became aware of something else. A slow, deliberate movement around the edges of the sea. A second viewing field focused in on one particular section, and Herb was momentarily thrown by the contrast within his range of vision, between the quiet calm of his lounge-the polished wood sculpture and the white vase with the gentle pattern of flowers embossed around the rim, the parquet floor and the cool eggshell finish of the ceiling-and the frantic battle outside. In the midst of the calm of his lounge, there on the viewing field, he could see the little machines outside forming themselves from the sea of metal, sucking its material as they bulged and then split into two.

“Reproducing once every eight point two seconds,” said Robert. “Pretty impressive really. Well, when you consider the limitations of the intelligence we’re up against.”

“They’re going to surround us,” whispered Herb. “We’ll be trapped.”

It seemed inevitable. He could see the thickening cloud of the tiny machines as they rose into the air, an angry cloud of insects that seemed to pull a silver curtain up from the surface, such was their density-a silver curtain that promised to engulf them. It was as if a sack was being lifted up and around and over the ship.

“Shouldn’t we run now?” asked Herb.

Robert shook his head. “Don’t worry. I’ve worked out their rate of reproduction. We’ll get away with fourteen seconds to spare.”

Herb said nothing to that. There was nothing to say. All he could do was sit and stare at the rising cloud of little machines, each about the size and shape of a saucer. They spun and shimmered in the virtual light. Their underside was darker than the top and scored with a series of concentric circular grooves. When they fissioned, it was into two saucers joined along their tops, grooved undersides facing outward.

“How do they know we’re here?” asked Herb. “I thought we were masquerading as friends?”