The Cavallino Bianco is a famous hotel in a charming location near the lake of San Wolfango. The owner, Gioseffa, unsuccessfully courted by Leopoldo, her first waiter, is infatuated with the lawyer Bellati, a regular customer of the hotel, for whom she always reserves the best room. Arriving at the hotel, however, Bellati finds his room already assigned to Petronio Bottazzi, a Bolognese industrialist, and his daughter Ottilia, with whom he immediately falls in love, arousing an insane jealousy in Gioseffa's heart who fires Leopoldo, guilty of annoying her with his constant offers of love. To complicate the situation comes Sigismondo, son of Bottazzi's rival and pretender - for economic reasons - to Ottilia's hand; but the arrival of Claretta, daughter of Professor Hinzelmann, makes him forget Ottilia. A flirtation arises between the two, also favored by the complicity of Ottilia and Bellati.
There is a big party at the Cavallino Bianco: even the Archduke of Austria arrives. Leopoldo, immediately recalled to the hotel to help with the preparations, is the protagonist of a big scandal. Due to the jealousy he has towards Gioseffa, he takes his revenge by inviting the Archduke to leave the hotel which, he says, is not worthy of hosting him. The latter, with great good nature, makes it clear to the innkeeper how much Leopoldo is in love with her. Gioseffa, now convinced, implements the Archduke's advice: she fires Leopoldo as head waiter and hires him as her husband.