Jean est marinier. Il vit sur son piètre bateau, près d’un cimetière de péniches sur un affluent de la Seine appelé « bras-mort ». Il est amoureux de la fille d’un richissime armateur. La jeune femme lui retourne son affection mais se heurte violemment aux préjugés de classe de sa famille. En effet, ses parents tentent tout leur possible pour séparer les deux amants…

Jean Michaut is a bargeman who lives nearby an old barge cemetery named "Bras-Mort". He is in love with Monique, the daughter of a wealthy boat owner. The girl returns his affection but runs her head against the wall of her family's class prejudices. Her "nearest and dearest" prove indeed prepared to do everything to separate the two lovers. But Monique will not buy in. On the contrary, she leaves her intolerant family to live with Jean among simple, more tolerant bargemen.