The novel opens with Elena Greco receiving a phone call from Rino, the adult son of her lifelong friend Lila Cerrullo (also known as Raffaella and Lina). Lila has been missing for two weeks, and even though his mother has a history of erratic behavior, Rino is concerned. Elena is dismissive and unsurprised: Lila has often expressed her desire to vanish. A few weeks pass, and Lila has still not returned, prompting Elena to tell Rino to search the house. He notices that everything associated with his mother has vanished. Elena is frustrated with Lila's dramatic attempt to wipe out her existence, and begins writing the history of her friendship with Lila.
The Prologue establishes the frame narrative through which the rest of the story will be conveyed. Elena is motivated to write the history of her relationship with Lila as a reaction against Lila's attempt to erase her identity and history. This frame establishes the ambivalent and often tense relationship between the two women, a pattern which can be traced back to their earliest interactions. Elena and Lila clearly play an important role in each other's lives, since Elena is the person Rino reaches out to about his mother's whereabouts. However, it is unclear whether their relationship is uniformly positive. Elena is not worried about her friend; she seems instead to be frustrated and even annoyed.
The frame narrative serves to create suspense. Within Lila's childhood and adolescence, there may be clues about how and why she has disappeared. Readers also desire to know what events have shaped the friendship between the two main characters, since it has endured for most of their lives. This structure adds additional interest and significance to their childhood interactions.
Because of the prologue, readers know that the story of the friendship is being narrated from Elena's point of view, and also composed during a time when Elena feels angry towards her friend. This highlights the possibility that throughout the story, Elena may not be an entirely reliable narrator. She may be omitting or highlighting certain details in order to make Lila appear a certain way. Even if Elena is attempting to be as objective as possible, she will be limited in her knowledge of Lila's thoughts and feelings. While the story is meant to help readers understand and possibly solve the mystery of Lila's disappearance, it is also going to reinforce Lila's status as an enigma.
The Prologue also creates further ambiguity around the subsequent narrative by making it clear that the story of Elena and Lila's friendship is being narrated retrospectively. Elena is recalling the events of their childhood many years later, and her memories may not always be accurate. It is also unlikely that she can prevent later events and knowledge from shaping the impressions she conveys about Lila as a child.