Alain is the only son of a wealthy bourgeois couple. He takes violin lessons in Ménilmontant, where he is spotted by Fleur, a poor girl: she is going to kidnap him and demand a ransom from the young man's parents, money which will be used to pay for a good lawyer for her brother accused of killing a policeman.

The love affair of an ex-convict with a showgirl, unleashes the jealousy of his older, wealthy and unbalanced wife. A murder plot, staged phoney suicide and other twists and turns follow.

The film narrates the encounter between "La Tigra", a woman known by that nickname in the cafes of the port area for her character and her sharp claws, and Luis, a student of Fine Arts. There will be born a strong, passionate and necessarily brief relationship during which each of them will peek into the world of the other, until then unknown, unable to overcome the hostility of the same. Luis is unwilling or unable to leave his bourgeois stability and "La Tigra" is unable to leave an environment in which the malevo Olivera is the dominant figure.

Emma Zunz, who is planning a crime, intends to get away with it by presenting an audacious alibi.