Der Rosenkavalier ("the knight of the Rose") is set in mid 18th-century Vienna, but the music is dominated by the lilting waltz rhythms of late 19th-century Vienna. The plot centers around the shifting romantic attachments of four characters: the Marschallin (a beautiful, but aging noblewoman), Octavian (a young count who is in love with her), Baron Ochs von Lerchenau (a country bumpkin who isn't quite as young as he thinks he is), and Sophie (a young woman, to whom Baron Ochs is engaged). As the opera begins, the Marschallin and Octavian are together, having spent the night in lovemaking. Octavian is forced to disguise himself as a chambermaid by the announced arrival of a guest, but the guest is not the Marschallin's husband, as feared, but rather Baron Ochs. Ochs asks for the Marschallin's help in courting Sophie, but while she isn't looking, he makes a pass at the chambermaid, really Octavian in disguise. Octavian escapes, and in his absence, he is appointed as a Rosenkavalier, whose duty it is to carry the Baron's love-token--a silver rose--to Sophie. When Octavian carries out this mission, he and Sophie fall immediately in love, and Sophie aks him to save her from marriage to Ochs. After several dozen more plot twists, Ochs is confounded, the young lovers are united, and the Marschallin, who knew Octavian would eventually leave her for a younger woman, is left alone.