Paris 1847. A British Lord, Lord Henry Seymour, is famous for his eccentricities. The aristocracy disapproves of his frequenting of the dregs of society and his support of destitute people. On the other hand, his good looks attract beautiful women like Virginie, the star of the Prado, and Anna Risomonti, a fair Italian opera singer. As for Henry, he has designs on young but willful Chantereine, a young singer-actress. But Don Juan soon turns into Romeo and true love unites the couple. Unfortunately, Henry's life is thrown awry by fellow aristocrats, among whom Harel, his sworn enemy, who reveals the secret of his birth.

Lord Seymour, dandy notoire, se plaît sous le règne de Louis-Philippe à fréquenter les bas-fonds. Il a acquis une popularité évidente et sa hardiesse émerveille le Cercle des Lions. Dans les salons, les femmes l'entourent, mais il jette son dévolu sur une gentille danseuse et le peintre Geoffroy favorise ces fraîches amours. Les excentricités du lord produisent leur fruit. Son dévouement à la plèbe s'exprime dans des pamphlets. L'aristocratie réagit, révèle le secret de sa naissance. Seymour est un bâtard que le roi se doit d'exiler.