The names in the book are real. So are the events. Events that cover thirty years, some of which have remained in history as "wonderful" because they shook and changed the course of Physics and opened new windows for the perception of the world. At the same time, they were years of dramatic military and political developments in Europe, with an impact on the whole world. In these years, two young physicists meet and a friendship is formed between them, which only death could break. They follow the same path and share the same interests. Both Jews, without an academic family background and unconventional. They love music and their happiest moments are when they play duets. Paul Ehrenfest on the piano and Albert Einstein on the violin. Especially after discussions on hot problems of theoretical physics...