A masked bandit steals valuables from Commendatore Anzaloni's apartment and flees, leaving Anzaloni unharmed. Inspector Ingravallo is called in. The robbery is suspicious; the thief found the jewellery too quickly. The neighbour, Liliana Banducci, employs a servant girl, Assuntina. Her fiancé, Diomede, tries to flee when he sees police tailing Assuntina.