It all begins on the day that Sophie Amundsen, a fifteen-year-old girl, finds in her box a letter addressed to her, on which is written only one sentence: "Who are you?" A second envelope reaches her, and inside a new word: "Where does the world come from?" Sending these letters remains a mystery, but the questions asked intrigue Sophie. It is the beginning of a strange correspondence that will plunge the girl in search of answers in a long visit of the main figures of philosophy...