Diana, Countess de Belfort, late at night entering the hall of her Neapolitan palace, finds there two men cloaked in cloaks, who hastily hide when she appears. Intrigued and angry, Diana orders a butler, but he justifies his ignorance by the fact that he went to bed early. Here comes one of the servants, Fabio, whom Diana sent after the perpetrators of the commotion, and reports that he saw one of the uninvited guests when he, running down the stairs, threw his hat into the lamp. Diana suspects that it was one of her rejected admirers, who bribed a servant, and, fearing the publicity, which, according to the customs of the 17th century, would have brought ill fame to her house, ordered to immediately wake up and send all the women to her. After a strict interrogation, perpetrated by chamberlains, who were extremely dissatisfied with what was happening, but hiding their feelings, the countess managed to find out that the mysterious visitor was her secretary, Theodoro, who had a crush on cameraman Marcela and came to see her. Although Marcela fears the hostess’s wrath, she admits that she loves Theodoro and, under the pressure of the countess, recounts some of the compliments that her lover gives her. Upon learning that Marcela and Teodoro are not averse to getting married, Diana offers to help young people, because she is very attached to Marcel, and Teodoro grew up in the Countess’s house and she has the highest opinion of him. However, left alone, Diana was forced to admit to herself that the beauty, intelligence and courtesy of Theodoro were not indifferent to her and, if he were a noble family, she would not resist the merits of a young man. Diana is trying to suppress the unkind envious feelings, but the dreams of Teodoro have already settled in her heart.

Meanwhile, Theodoro and his faithful servant Tristan are discussing the events of last night. The frightened secretary is afraid to be driven out of the house for her romance with the chamberlain, and Tristan gives him wise advice to forget her lover: sharing his own worldly experiences, he invites the owner to think about her shortcomings more often. However, Theodoro resolutely does not see any flaws in Marseille. At this moment, Diana enters and calls on Theodoro to draft a letter for one of her friends, offering as a model several lines sketched by the countess herself. The meaning of the message is to reflect on whether one can "ignite with passion, / seeing someone else's passion, / and be jealous, / not yet in love." The Countess tells Theodoro the story of her friend’s relationship with this person, in which her relationship with her secretary is easily guessed.

While Teodoro composes his own version of the letter, Diana tries to find out from Tristan how his master spends his free time, by whom and how much he is passionate. This conversation is interrupted by the arrival of the Marquis of Ricardo, the longtime admirer of the Countess, vainly seeking her hand. But this time, the charming countess deftly avoids a direct answer, referring to the difficulty of choosing between the Marquis of Ricardo and Count Federico, his other faithful admirer. Meanwhile, Theodoro composed a love message for the fictional friend of the countess, who, in Diana’s opinion, is much more successful than her own version. Comparing them, the countess shows an unusual ardor for her, and this leads Theodoro to the idea that Diana is in love with him. Left alone, for some time he is tormented by doubts, but gradually penetrates with confidence that he is the subject of the passion of his mistress, and is ready to answer her, but then Marcela appears happily telling her lover that the countess promised to marry them. Theodoro's illusions instantly crumble.Suddenly, Diana, who entered, finds Marcel and Teodoro in each other's arms, but in response to the young man’s gratitude for the generous decision to meet the feelings of two loving countess, she irritably orders the maid to be locked up so as not to set a bad example for other maids. Left alone with Theodoro, Diana asks her secretary if he really intends to marry, and, having heard that the main thing for him is to cater to the countess's wishes and that he could completely do without Marcela, clearly makes clear to Theodoro that she loves him and that only estate prejudices impede the unification of their destinies.

Dreams take Teodoro high: he already sees himself as the countess’s husband, and Marcela’s love note not only leaves him indifferent, but causes irritation. The young man is particularly offended that a recent lover calls him "his spouse." This annoyance falls upon Marcel herself, who managed to leave her impromptu prison. There is a stormy explanation between the recent lovers, followed by a complete break - it is needless to say that Teodoro becomes its initiator. In revenge, the wounded Marcela begins to flirt with Fabio, in every possible way swearing at Theodoro.

Meanwhile, Count Federico, a distant relative of Diana, seeks her favor with perseverance no less than the Marquis of Ricardo. Having met at the entrance to the temple where Diana entered, both admirers decide to directly ask the beautiful countess which of them two she prefers to see as her husband. However, the countess deftly avoids the answer, again leaving her fans in limbo. However, she turns to Theodoro for advice on which of the two she should prefer. In fact, this, of course, is nothing more than a trick, with the help of which Diana, without binding herself with specific words and promises, wants to make clear again to the young man how passionately he is loved by her. Irritated by the reverence of her secretary, who does not dare to be completely frank with her and is afraid to reveal her feelings to her, Diana orders to announce that she is marrying the Marquis of Ricardo. Teodoro, hearing about this, immediately makes an attempt to make peace with Marcela. But the girl’s insult is too great, and Marcela cannot forgive her former lover, although she continues to love him. The intervention of Tristan, the servant and attorney of Theodoro, helps to overcome this barrier - young people make peace. This is greatly facilitated by the fervent rejection of Theodoro by all Marcela’s jealous accusations and how disrespectfully he speaks of Countess Diana, who, unnoticed, is silently present at this scene. Outraged by the treachery of Theodoro, the countess, leaving her hiding place, dictates a letter to the secretary, the meaning of which is completely transparent: this is a sharp rebuke to an ordinary person who deserved the love of a noble lady and who failed to appreciate it. This unequivocal message again gives Theodoro an excuse to abandon Marcela’s love: he on the go thinks up “that the countess decided to marry off her cameraman as Fabio. And although Marcela’s offense is limitless, the smart girl understands that everything that happens is a result of changes in the countess’s mood, which she does not dare to enjoy Theodoro’s love, because he is a simple man, and she is a noble lady, and does not want to give him up to Marcela. Meanwhile, the Marquis Ricardo appears, happy that she will soon be able to call Diana his wife, but the countess immediately cools the enthusiasm of the ardent bridegroom, explaining that a misunderstanding had occurred: the servants simply misinterpreted her warm words about the Marquis, and again, again, between Diana and her secretary, there was a complete omission of explanation, during which the countess sharply points out to her secretary the divide between them. Then Theodoro says that adores Marcela, for which he immediately gets a slap in the face.

Count Federico, who guesses a completely different feeling behind Diana’s fury, becomes an accidental witness to this scene. The count dedicates the Marquis of Ricardo to his discovery, and they plan to find a hired killer to get rid of Theodoro. Their choice falls on Tristan, the servant of Theodoro, who, for a great reward, promises to save the Count and Marquis from a happy rival. Upon learning of such a plan, Theodoro decides to go to Spain in order to save his life and be cured in the distance from his love for Diana. The countess approves of this decision, cursing with tears the class prejudices that prevent her from connecting life with her loved one.

The way out is Tristan. Upon learning that one of the noble people of the city, Count Ludoviko, twenty years ago lost a son named Theodoro - he was sent to Malta, but was captured by the Moors - a clever servant decides to pass off his master for the disappeared son of Count Ludoviko. Dressed as a Greek, he penetrates under the guise of a merchant into the Count's house - there is no limit to the happiness of the elderly Ludoviko. He immediately rushes into the house of Countess Diana to hug Theodoro, in which, without any hesitation, he immediately recognizes his son; Diana is happy to declare her love to everyone. Although Theodoro honestly confesses to the Countess that he owes his unexpected exaltation to Tristan's dexterity, Diana refuses to take advantage of Theodoro's nobility and is firm in her intention to become his wife. Fortunately, Count Ludovico has no limits: he not only found a son, but also found a daughter. Marcela receives a good dowry, she is extradited as Fabio. Tristan does not remain forgotten: Diana promises him her friendship and patronage if he keeps the secret of the rise of Theodoro, she herself will never again be a dog in the manger.