Twelve-year-old Bobby Nusku catalogues traces of his mother's life and waits for her to return home. Bobby thinks that he's been left to face the world alone until he meets lonely single mother Val and her daughter Rosa. They spend a magical summer together, discovering the books in the mobile library where Val works as a cleaner. But as the summer draws to a close, Bobby finds himself in trouble and Val is in danger of losing her job. There's only one thing to do – and so they take to the road in the mobile library.