The Prologue establishes several key relationships that will remain central to the plot. Caitlin is secondary to her sister, especially for her parents. Mr. and Mrs. O’Koren focus their attention only on Cass, ignoring Caitlin and not acknowledging her birthday. Additionally, Caitlin’s parents don’t see that she has a cut on her face, which is a key foreshadowing of the injuries that are to come. Despite the way her sister’s disappearance is posed to negatively impact her, Caitlin feels strongly about her connection with her sister, reflecting on how Cass “would never have forgotten [Caitlin’s] birthday” (5).