Titus Vespasian, Emperor of Rome, has succeeded to the throne that his father, Vespasian, usurped from the Emperor Vitellius. Vitellia, daughter of Vitellius, urges her boyfriend Sextus to join the conspiracy against Titus and his consort Berenice. Sextus, however, is loyal to Titus. The other players include Annius, Sextus`s friend; Servilia, Sextus`s sister; and Publius, captain of the guard. When Sextus sees the Capitol in flames, he runs to save Titus, but thinks himself too late when he comes upon a dying man wearing the royal purple. Sextus prepares to kill himself, but Annius tells him it is the conspirator Lentulus who is disguised in the robes. Sextus exchanges cloaks with Annius, since his own bears the badge of the conspirators. Unfortunately, this means that Annius is arrested for treason. He is willing to take the fall for Sextus, but the dying Lentulus tells the truth, Annius is freed, and Sextus is arrested. Sextus, too, maintains silence to protect Vitellia.