Donovan couldn’t recall how long he’d been walking through the hot summer heat of southern Appalachia. All he knew was that he’d transversed roughly 300 miles (about 483 kilometres) of rugged terrain, starting in what had once been the city of Roanoke, Virginia and ending in the mountainous region of what was formally called North Carolina.

Only one year earlier, a mammoth asteroid had slammed into Earth. Of the world’s 8 billion human inhabitants, it was thought that only 2 million survived. These days, though, no one could be certain of the exact toll, for the remaining inhabitants were more concerned with day-to-day survival then with tabulating such now-meaningless figures.