It was now five in the afternoon, the sun low over the rise of Syrtis, the temperature plummeting past zero, on its way far down. As the faster walkers, mostly natives and the latest immigrants, pressed on ahead, the crowd became a long column. The people in rovers reported that it was several kilometers long now, and getting longer all the time. These rovers drove up and down the line, picking people up and sometimes letting others out. All available walkers and helmets were being used. Coyote had appeared on the scene, driving up from the direction of the dike, and seeing his boulder car, Nadia instantly suspected he was behind the broaching of the dike; but after greeting her cheerily over the wrist, and asking how things were going, he drove back toward the city. “Get South Fossa to send a dirigible over the city,” he suggested, “in case anyone was left behind, and is up on the mesa tops. There must be some people in there who slept through the day, and when they wake up they are in for one very big surprise.”

He laughed wildly, but it was a good point, and Art made the call.

Nadia walked along at the back of the column with Maya and Sax and Art, listening to reports as they came in. She got the rovers to drive on the dead piste, to avoid kicking dust into the air. She tried to ignore the fact that she was tired already. It was mostly lack of sleep, rather than muscular exhaustion. But it was going to be a long night. And not only for her. Many people on Mars were entirely city dwellers now, and unused to walking very far at a time. She herself seldom did, though she was often on her feet around construction sites, and did not have a desk job like many of these people. Luckily they were following a piste, and could even walk on its smooth surface if they cared to, between the suspension rails on the edges and the reaction rail running down the middle. Most preferred to stay on the concrete or gravel roads running alongside the piste, however.

Unfortunately, walking out of Isidis Planitia in any direction but north meant walking uphill. Libya Station was about seven hundred meters higher than Burroughs, not an inconsiderable height; but the grade was almost continuous over the seventy kilometers, and there were no steep sections anywhere along the way. “It will help keep us warm,” Sax muttered when Nadia mentioned it.

It got later and later, until their shadows were cast far to the east, as if they were giants. Behind them the drowning city, lightless and empty, black-floored, disappeared over their horizon mesa by mesa, until finally Double Decker Butte and Moeris Mesa were submerged by the skysill. The dusky burnt umbers of Isidis took on more and more color, and the sky darkened and darkened, until the fat sun lay burning on the western horizon, and they walked slowly through a ruddy world, strung out like a ragtag army in retreat.