The film tells a melodramatic story of thwarted romance, set against a background of the Marseille docks, and experiments with many techniques of camerawork and editing.

She is desired by Petit Paul (Edmond van Daële), a thuggish layabout, but is secretly in love with Jean (Léon Mathot), a dockworker.

Epstein had been much impressed by Abel Gance's recently completed La Roue, and in Cœur fidèle he similarly applied rhythmic editing, overlays, close-ups, and point-of-view shots.

The opening sequence establishes Marie's situation in the harbour bar through montage: we see close-up images of her face, hands, and the table and glasses she is cleaning.

The film's most celebrated sequence, set at a fairground, employs rhythmic editing to chart the escalating tension of the love triangle.

Cœur fidèle is one of several early films to use the location of the Marseille dockside (in the wake of Louis Delluc's Fièvre, and looking forward to Alberto Cavalcanti's En rade), and the evocative images of looming ships and deserted wharfs contribute to a style which would be characterized over the next decade and a half as "poetic realism" (cf.