I thought I lost you

this story is about Katherine Bergman and her best friend Alexander Teed. Katherine was never a social butterfly not at all, all she ever had by her side was her sister Allyson and of course, Alex. when Alex and his family had gone away to move. Katherine was devastated. Alex didn't tell her where they moving. In fact the only thing that he did leave was a necklace and a promise. A promise saying that they would find each other. but the question is, how? there are a million places on earth to begin with, and there chances of finding each other is one in a million.