It started as an assignment. Everyone in Caitlin's class wrote to an unknown student somewhere in a distant place. All the other kids picked countries like France or Germany, but when Caitlin saw Zimbabwe written on the board, it sounded like the most exotic place she had ever heard of -- so she chose it. Martin was lucky to even receive a pen pal letter. There were only ten letters, and forty kids in his class. But he was the top student, so he got...