On September 1, 1950, at the dawn of the Cold War, the Italian physicist Bruno Pontecorvo and his family mysteriously disappeared. This created a real political earthquake in Europe and the USA: Pontecorvo was in fact a scientist known around the world for his expertise in a very delicate area, that of nuclear research. The story of his disappearance is one of the most fascinating mysteries related to the atomic era, especially when it became known that he had crossed the Iron Curtain and moved to Soviet Union. Bruno Pontecorvo's unique life was strongly interlaced with 20th century history and with the development of particle physics. With his exceptional theoretical intuitions, which went hand in hand with his brilliant qualities as an experimental physicist, Bruno Pontecorvo is the scientist that, more than anyone else, has entered the secrets of the most elusive and enigmatic particle of our universe, the neutrino.