Cato, a Tragedy takes place in Utica, Tunisia, in the African kingdom of Numidia, during Julius Caesar’s reign over the Roman Republic. Two brothers, Portius and Marcus, enter and say that it is an “important day, big with the fate / Of Cato [their father] and Rome” (5). The two men lament Caesar’s tyrannical reign, saying he has “ravaged more than half the globe” (5), and ask what their father Cato, who fled to Utica and now there directs a “feeble army, and an empty senate,” can do to stop him (6). Marcus, however, is also thinking of his other griefs, telling Portius of his “successless love” with a woman named Lucia (6). In an aside, Portius reveals that he is in love with Lucia as well, saying, “Thou see’st not that thy brother is thy rival; / But I must hide it for I know thy temper” (6).

Marcus is asking Portius why he does not feel more badly for his blight when the senator Sempronius enters. Sempronius immediately reveals in an aside that he does not like Portius and must lie about his intentions: “I like not that cold youth.