Raphael a restaurant mandolin player with a limp, a father to support, and a lot of debt, accepts a job offered by his friend, Giardino, to play a serenade under an apartment window at the behest of a mysterious blonde. As he’s playing, a man high up on a balcony is pushed to his death. The apartment belongs to a famous conductor who promises to help Raphael’s musical career if he can find out who the blonde was so the musician pays a call on Giardino only to see him come sailing out the window. Raphael soon finds himself up to his neck in murder, gangsters, blackmail, and a long-ago crime dating back to World War II when he becomes involved with the maestro’s daughter-in-law (Ornella Muti), a nurse at a nearby mental hospital..
