Vacationing in Bad Ischl, archduke Ludwig, the Austrian emperor Franz- Joseph's brother and empress Elizabeth's (Sissi) brother-in-law, falls in love with Luise Pichler, a schoolmistress. At the same time, lieutenant Zauner, his aide, loses his heart to Mizzi, a baker's daughter. Complications arise when Ludwig introduces himself as Zauner: under the assumption that only financial concerns stop her lieutenant from marrying her, Luise goes to Vienna to seek help from the empress. Sissi tells the girl the truth. Luise renounces her love for Ludwig, while the real lieutenant Zauner gets married to his Mizzi.