A disguised bandit steals valuable jewellery from Commendatore Anzaloni's apartment and flees, leaving Anzaloni unharmed. Inspector Ingravallo investigates and finds that the robbery is suspicious in that the robber was able to find valuables too quickly. A neighbour, Liliana Banducci, employs a servant girl, Assuntina. Her fiancé, Diomede, tries to escape when he sees police tailing Assuntina. But Diomede has an alibi. Liliana's cousin, Dr. Valdarena, pays her a visit, only to find her corpse on the floor. But before calling police, Valdarena removes an envelope addressed to him from the sideboard. Liliana's husband Remo was away from Rome at the time of the murder, but he is very surprised to hear that Liliana had changed her Will (law) only one week earlier''.