The story is told in the form of letters exchanged between fifteen-year-old girls, Mandy and Tracey. They begin writing after Tracey places an ad in fictional magazine GDY. The two girls share information about their lives from school, to family, to relationships. Mandy reveals that her brother is abusive and violent, information which Tracey tries to ignore. It appears to Mandy that Tracey's life is perfect, as she has a wonderful boyfriend, rich and caring parents, and she is close to her siblings. However, inconsistencies start appearing in Tracey's letters, and when Mandy questions her on them, Tracey stops writing. Mandy refuses to give up, and finally Tracey replies with the information that she is in fact in a juvenile detention center, and will be there for a long time. Tracey expects Mandy to no longer want to write to her, but Mandy continues to do so. Their relationship becomes even deeper now that they are completely honest with each other. Mandy, however, occasionally frustrates Tracey with her naivete as Tracey claims she is not as "nice" as Mandy claims, and becomes angry when Mandy makes a joke about tunneling into her cell and staying with her. Throughout their letter writing, Tracey seems to get in touch with her "softer" side, which includes writing an essay about her Nanna. She wins an award for the story, and asks Mandy to celebrate for her. Towards the end of the book, Tracey finally confesses the truth about her family and gives her reason for not wanting to hear about Mandy's brother. Mandy never replies to the letter and never writes again. Tracey continuously writes, getting increasingly worried, especially when her letters are sent back to her with "Return To Sender" on them, not in Mandy's handwriting. Tracey continues to write, though she now knows no one is reading her letters.It is never explicitly stated what happened to Mandy, however John Marsden says that if you read Mandy's last letter and Tracey's description of her dream, the reader should be able to figure it out.