I am the sister who didn't go to war. I can only tell you my side of the story. Hallie is the one who went south, with her pickup truck and her crop-disease books and her heart dead set on a new world.
This quote opens the second chapter of the novel, which is the first chapter narrated by Codi. The first word of the quote is "I," emphasizing the first person narration. In addition, the second line explains the subjective nature of a first person narration, anticipating any criticisms that we might make of the novel as a whole on that account. This opening also foreshadows Hallie's death. The insistence that the story will be one-sided suggests that Hallie will be not only absent but not capable of telling her side of the story. The phrase "going south"—while used here directly to refer to Hallie's literal trip south form Arizona to Nicaragua—is also a colloquial metaphor for dying. Hallie's heart is described as not just "set" but "dead set," again associating her trip with her death. Although Hallie will never become integrated into the primary plots of the novel, she will haunt it from beginning to end.