Ana Maria loves a modest guitar player, Júlio; when she herself in a 'retiro' (typical fado tavern), public and critics rend major applause. Fame brings about new friends, namely bohemian young who play and sing the fado with her, and not so young men but who rich and powerful enough to patronize her, promote her, and wish to become intimate with her. Júlio the guitarist feel betrayed, and he sets his mind to depart to the African colonies, to leave her forever. Knowing that he's going to embark, Ana Maria's heart between her first love, and the appeal of the rich and famous.

The great fadista, Amelia Rodrigues, made her screen debut in Capas Negras, which took its name from the black capes worn by the students in the university city of Coimbra, where the film is set. The action begins in a tavern where a group of former students are reminiscing about their time at the university. One of the students, Jose Duarte then breaks into song, performing an impromptu fado in the local Coimbra style. The tavern owner's niece, the aptly named Maria Lisboa promptly retaliates with a fado of the Lisbon variety. The melodramatic plot then centers on the frustrated romance between these two characters, and the soundtrack is essentially a musical duel between these two different styles of Portugal's national song.