Prologue The famous Neapolitan actress Silvia Lombardi was rudely awakened in the middle of the night. A masked intruder broke into her room, kissed her passionately and tried to kidnap her. But the incident came to an abrupt end: alarmed by a noise, the man jumped out of the window. Silvia shouts for help.

Act I In the meantime, the entire city of Naples has heard what happened. It is also a subject of gossip for the models in the fashion house “La bella di Napoli”. The only one who cannot understand why such a fuss is being made over a simple kiss is Louise from Paris. The fashion designer and owner of the business, Andrea Coclé, wants to hear nothing more about it. Alone, he passionately declares his love in front of a tailor’s dummy made to look like Silvia: he is head over heels in love with the actress. Silvia, for her part, loves Andrea’s fashionable creations more than anything and pays him a visit at his studio. Their flirting is interrupted by a sensationalist reporter, Sam Borzalino, who is writing an article about the break-in at Silvia’s villa and wants to interview her. Andrea shows him the door and has Silvia try on a new dress. The next interruption is caused by Caretto, the police minister, who is investigating the break-in. He questions Andrea more closely, eventually leading him to admit that he was in the garden of Silvia’s villa at the time the crime is alleged to have been committed. He says he sang her a serenade, but instead of using his voice he sang it with his soul – a silent serenade. As a result of this suspicious behaviour, Andrea is arrested for the attempted abduction of Silvia and threatened with the death sentence.

As he continues his investigations in the fashion house, Sam encounters Louise. The two of them fall in love with one another.

Silvia pays a visit to her fiancé, the Neapolitan head of government Benedetto Lugarini, and tries to persuade him to pardon Andrea. But when he hears that the crime was a kiss he refuses. Besides, he is furious that the newspapers are full of stories about the break-in at Silvia’s villa while not a word is said about the failed bomb attack carried out the previous night in an attempt to kill him. He asks Caretto to give the search for “his” offender priority over Silvia’s case.

Caretto learns that, to mark his birthday, the King of Naples intends to pardon the man who attacked Lugarini. The police minister wants to use this information to persuade Andrea Coclé to confess to both crimes – this would allow him to say that he has solved the case and at the same time save Andrea’s life. But it takes a re-enactment of the kiss with Silvia, which makes the actress certain beyond any doubt that the fashion designer is the culprit, before Andrea agrees to the plan.

Act II At the trial to establish Andrea’s guilt all the protagonists encounter one another: Silvia, Andrea, Lugarini, Caretto, Louise and Sam.

To make himself plausible as the bomber, Andrea yells out various slogans, inciting the hatred of Lugarini but also the approval of the people of Naples who are also in the courtroom. And the fashion designer is indeed found guilty and sentenced to death. His last request is an evening meal with Silvia, which the actress agrees to. This leads to a violent quarrel with the jealous Lugarini, and the couple break off their engagement.

Andrea and Silvia have dinner together and finally declare their love for each other. But the romantic mood is destroyed by Caretto who brings disastrous news for Andrea: the King of Naples has suddenly died and had not yet signed the pardon. Now Andrea really is under sentence of death. And there can be no hope of a second pardon, because none other than Lugarini has declared himself the new regent of Naples.

However, the townsfolk have not forgotten Andrea’s performance in court: By means of a revolution the hated Lugarini is removed from office and, miraculously, the alleged assassin Andrea is made new regent of Naples. Although this means that the fashion designer has escaped death, his conscience plagues him nonetheless: after all, he did not commit either of the crimes he was accused of.

Fortunately, the real bomber comes to see him and insists on being made head of government as a reward for the planned assassination. So far, so good. But what if the real intruder in Silvia’s villa comes forward and, with passionate kisses, asserts his right to the actress?

Luckily, it turns out that Silvia sleepwalks and both the kiss and the attempted abduction were only a dream. Andrea is overjoyed and has nothing more to fear.