"If you say so," Ouellette said at last.

Miri gaped for more.

They plotted their course by derelict road signs and inboard maps. Ouellette steadfastly refused to go online. Clarke had to wonder at the stops marked along their route. Belfast? Camden? Freeport? They'd barely been dots on a map even before the world ended: why not go to Bangor, just a few klicks to the north? That was where the people would be.

"Not any more," Ouellette said, raising her voice above a frenetic orchestral seesaw she’d attributed to some Russian maniac called Prokofiev.

"Why not?"

"Cities are the graveyard of Mankind." It had the ring of a quote. "There was this threshold, I don't remember what it was exactly. Some magic number of people per hectare. Any urban center was way up on the wrong side of it. Something like ßehemoth, set loose in a high-density urban area—not to mention all the ancillary pathogens that hitched a ride in its wake—it takes off like a brush fire. One person sneezes, a hundred get sick. Germs love crowds."

"But small towns were okay?"

"Well, not okay, obviously. But things didn't spread as fast—the spread's still going on, actually. The towns were small and seasonal, and the areas in between were pretty much owned by the whitecaps." Ouellette gestured at the withering foliage scrolling past the windshield. "This was all privately owned. Rich old rs and Ks who didn't mingle, had good medical. They're gone now too, of course."

Gone to Atlantis, Clarke surmised. Some of them, anyway.

"So the big cities had exactly two choices when Firewitch came calling," Ouellette continued. "They could either throw up the barricades and the static-field generators, or they could implode. A lot of them couldn't afford generators, so they imploded by default. I haven't been to Bangor since fifty-three. For all I know they never even cleaned up the bodies."

They got their first live customers at Bucksport.

They pulled off the main drag at about two a.m., next to a Red Cross Calvin cycler with a worrisome yellow telltale winking from its panel. Ouellette examined it by the light of an obsolete billboard, running on stored solar, that worked ceaselessly to sell them on the benefits of smart cloth and dietary proglottids.

"Needs restocking." She climbed back into Miri and called up a menu.

"I thought they got everything they needed from the air," Clarke said. That's what photosynthesis was, after all—she'd been amazed to discover how many complex molecules were nothing more than various combinations of nitrogen, carbon, and oh-two.

"Not trace elements." Ouellette grabbed a cellulose cartridge, its compartments filled with red and ochre paste, from the dispensing slot. "This one's low on iron and potassium."

The billboard was still hawking its nonexistent wares the next morning when Clarke squeezed herself into Miri's toilet cubicle. When she came out again, two silhouettes were plastered against the windshield.