In eighteenth-century Italy the Castrati recreated heaven on earth. Their exquisite voices soared above the glittering world of courtiers and nobility. Those who achieved fame were showered with riches and sexual favours, but their success also hid a terrible sadness. Tonio, of noble birth, is the victim of a vengeful brother. Disinherited and forced to join the ranks of the Castrati, he plans his revenge while striving to become the greatest of all singers. Guido, sacrificed to the knife at an early age, composes opera and dreams of the perfect voice to give it life. He discovers Tonio and becomes his teacher. As together they reach the very pinnacle of success, Tonio is pushed to the extremes of endurance as he tries to resolve his lust for glory, and for vengeance...