Cleopatra is a beautiful woman but has a small flaw: when she likes an officer of the guard, after a night of love she makes him poison by the trusted Tortul so that Marcantonio does not find out. Cesarino is a new officer, not yet aware of Cleopatra's little vice and immediately agrees to guard the queen. When she enters, however, she does not find the true sovereign, but Nisca, a slave her double who the perfidious Tortul had found to allow Cleopatra to go incognito to Marcantonio. But, after the first night, the real Cleopatra returns.