A prince falls in love with a barmaid during his last fling before assuming the crown.

At the royal palace in Karlsburg, King Ferdinand counsels his grandson, Prince Karl Franz, on the young man's imminent engagement to the wealthy Princess Johanna of Nordhausen. The king observes that although their country is poor, it has always survived because the men of the royal family marry well. The following evening, Johanna is feted with a ball, but she finds the prince's cold, formal manner off-putting. The king and Johanna's mother, Queen Mathilda, discuss the shaky prospects for an alliance between their heirs, and Mathilda says that Karl must learn to radiate warmth and charm. Karl's teacher, Prof. Juttner, is summoned to the palace in the middle of the night and ordered to instruct the prince in the graces of living. Juttner maintains that such an education comes from being with other people, and recommends that Karl be sent to his own alma mater, the University of Heidelberg. Karl is dispatched to Heidelberg the next day, along with Juttner and the punctilious royal valet, Lutz. They take rooms in an inn owned by Joseph Ruder, and Karl is immediately charmed by Ruder's pretty niece Kathie. When Karl impulsively kisses Kathie, however, she angrily rebuffs him. Classes begin, and the haughty prince bristles at being treated like all the other students. After chastening comments from Juttner and Kathie, however, Karl resolves to adapt to student life, and quickly finds that he enjoys it. On Kathie's recommendation, he joins the Westphalians, a student corps made up of good-natured commoners, and learns to consume prodigious amounts of beer. When Karl again attempts to kiss Kathie one evening, she knocks him down, as Lutz watches, aghast. Lutz orders Ruder to send Kathie away, threatening dire consequences if the incident is reported. The distraught Ruder goes to Kathie's room and finds her already packing, and tells her where to find a job in a nearby town. The following evening, the students protest Kathie's absence, and Ruder confides to Karl the name of the restaurant where Kathie now works. Karl goes to apologize, and when he causes Kathie to break some plates, she loses her job. Karl humbly beseeches Kathie to return to Heidelberg and declares his feelings for her. Now in love, Karl and Kathie return to Ruder's inn. One night, Karl is drinking and singing with the Westphalians when his true identity is accidentally revealed to the imperious Count Von Asterburg, head of the elitist Saxo-Borussian corps. Von Asterburg insists that the prince join their corps, and when Karl refuses to leave his Westphalian friends, challenges him to a duel. Karl defeats Von Asterburg in a sword fight, and the two men shake hands as friends, but Kathie is appalled. The lovers make up, and one night, at a carnival, Karl asks Kathie to go away with him. Before they can leave, however, Prime Minister Von Mark arrives from Karlsburg with the news that the king is ill and wishes to see Karl. After promising Kathie he will return, Karl returns to the palace. The king announces that Karl's marriage to Johanna will take place shortly, and when Karl protests that he is in love with Kathie, the king reminds him of his duty. Karl accuses Von Mark of having tricked him into returning, but the prime minister replies that the king is actually much sicker than he realizes. The king passes away, and preparations are made for Karl's marriage. While traveling to Nordhausen for the wedding, Karl suddenly orders the train to stop in Heidelberg. Karl goes to Ruder's inn, where he and Kathie lovingly say goodbye.