Lost in the Black Forest, Otto meets three mysterious sisters and finds himself entwined in a puzzling quest involving a prophecy, a promise, and a harmonica. Decades later, as the second World War approaches, the lives of three children -- Friedrich in Germany, Mike in Pennsylvania, and Ivy in California -- become interwoven when the very same harmonica lands in their lives. All the children face daunting challenges: rescuing a father, protecting a brother, holding a family together. Pulled by the invisible thread of destiny, their solo stories converge.