One morning Nell looked out the window and saw the world had turned the color of pencil lead. Cars, velocipedes, quadrupeds, even power-skaters left towering black vortices in their wakes. Harv came back from being out all night. Nell screamed when she saw him because he was a charcoal wraith with two monstrous growths on his face. He peeled back a filter mask to reveal grayish-pink skin underneath. He showed her his white teeth and then took up coughing. He went about this methodically, conjuring tangles of spun phlegm from his deepest alveoli and projecting them into the toilet. Now and then he would stop just to breathe, and a faint whistling noise would come from his throat.

Harv did not explain himself but went about working with his things. He unscrewed the bulges on his mask and took out black things that kicked up little black dust storms when he tossed them onto the floor. He replaced them with a couple of white things that he took from a Nanobar wrapper, though by the time he was finished, the white things were covered with his black fingerprints, the ridges and whorls perfectly resolved. He held the Nanobar wrapper up to the light for a moment. "Early protocol," he rasped, and pitched it toward the wastebasket.

Then he held the mask up to Nell's face, guided the straps around her head, and tightened them down. Her long hair got caught in the buckles and pinched, but her objections were muffled by the mask. It took a little effort to breathe now. The mask pressed against her face when she inhaled and whooshed when she exhaled.

"Keep it on," Harv said. "It'll protect you from toner."

"What's toner?" she mumbled. The words did not make it out through the mask, but Harv guessed them from the look in her eyes.

"Mites," he said, "or so they say down at the Flea Circus anyway." He picked up one of the black things taken from the mask and flicked it with a fingertip. A cineritious cloud swirled out of it, like a drop of ink in a glass of water, and hung swirling in the air, neither rising nor falling. Sparkles of light flashed in the midst of it like fairy dust. "See, there's mites around, all the time. They use the sparkles to talk to each other," Harv explained. "They're in the air, in food and water, everywhere. And there's rules that these mites are supposed to follow, and those rules are called protocols. And there's a protocol from way back that says they're supposed to be good for your lungs. They're supposed to break down into safe pieces if you breathe one inside of you." Harv paused at this point, theatrically, to summon forth one more ebon loogie, which Nell guessed must be swimming with safe mite bits. "But there are people who break those rules sometimes. Who don't follow the protocols. And I guess if there's too many mites in the air all breaking down inside your lungs, millions— well maybe those safe pieces aren't so safe if there's millions. But anyways, the guys at the Flea Circus say that sometimes the mites go to war with each other. Like maybe someone in Shanghai makes a mite that doesn't follow the protocol, and gets his matter compiler to making a whole lot of them, and sends them all across the water to New Atlantis Clave to snoop on the Vickys, or even maybe to do them harm. Then some Vicky— one of their Protocol Enforcement guys— makes a mite to go out and find that mite and kill it, and they get into a war.

That's what's happening today, Nell. Mites fighting other mites. This dust— we call it toner— is actually the dead bodies of all those mites."

"When will the war be over?" Nell asked, but Harv could not hear her, having entered into another coughing jag.

Eventually Harv got up and tied a strip of white Nanobar around his face. The spot over his mouth immediately began turning gray. He ejected used cartridges from his mite gun and inserted new ones. It was shaped like a gun, but it sucked air in instead of shooting things out. You loaded it with drum-shaped cartridges filled with accordion-pleated paper. When you turned it on, it made a little whooshing noise as it sucked air— and hopefully mites— through the paper. The mites got stuck in there. "Gotta go," he said, goosing the trigger on the gun a couple of times. "Never know what I might find." Then he headed for the exit, leaving black toner footprints on the floor, which were scoured away by the swirling air currents in his wake, as if he had never passed that way.