The night was cruel. A biting wind howled through the empty streets, cutting through Nathan’s thin coat like a blade. His fingers, stiff from the cold, clutched the small scrap of chicken he had managed to find—a rare meal after days of hunger.

But before he took a bite, he tore the piece in half and placed one part in front of the tiny shelter he had built days ago. It was nothing more than a few pieces of wood and cloth nestled against an abandoned wall, but it had been a home—for ...