Seventy-year-old Matthew Werner, who suffers from a debilitating case of Not Normal, doesn't know that nearly everyone on earth has died. He only knows that, out in the world, something terrible is happening - something he's not willing to discover. So he barricades himself inside and tries to stay ignorant. That is, until twelve-year-old Ruby Sterling shows up at his doorstep, all alone. The two have little in common. Matthew is old, strange, grumbly, and concerned only with figuring out what happened to his wife, who went missing months earlier. Ruby is serious, curious, and worried about the fate of her father and whether the future even exists. Neither wants much to do with the other. Which is why, when Ruby hears a voice on the radio telling people to come to a place called the Horizon, she's determined to find it, even if Matthew isn't. But outside, he's the least of her problems, and she's the least of his. To survive, they must count on the last thing either expected: each other. And the Horizon? It could be anywhere. Or nowhere at all.