In 1930s Berlin, choked by the tightening of Hitler's fist, the Klein family are gradually losing everything that is precious to them. Their fifteen-year-old daughter, Rosa, slips away on a Kindertransport train to begin a new life in England, vowing to secure a safe passage for her family. But as war breaks out and she loses contact with her parents, Rosa finds herself wondering if there are some vows that can't be kept...