To prepare a presentation on the topic of homelessness, Lou, a 13-year-old Parisian schoolgirl, meets Nora, a homeless 19-year-old who hangs out at the Austerlitz train station. Lou rapidly bonds with the homeless girl. Wanting to help Nora break her cycle of spending nights on the street, the introverted high school student invites her to come live with her family. But the arrival of this sassy young woman disrupts the daily lives of Lou's parents, who are still grieving for their baby daughter who died five years ago.