Poppaea, Nero's wife, who lusts after Marcus, devises a diabolical revenge for his rejection of her. Lygia is tied to a stake in the Circus and a wild bull is released into the arena. Lygia's bodyguard Ursus must attempt to kill the bull with his bare hands to save Lygia from being gored to death. Marcus is taken to the emperor's box and forced to watch, to the outrage of his officers, who are among the spectators. Ursus is able to topple the bull, though, and break its neck. Massively impressed by Ursus's victory, the crowd exhorts Nero to spare the couple. He refuses to do so, even after four of his courtiers, Seneca, architect Phaon, poet Lucan, and musician Terpnos add their endorsement of the mob's demands. Marcus then breaks free of his bonds, leaps into the arena, and frees Lygia with the help of the loyal troops from his own legion. Marcus accuses Nero of burning Rome and announces that General Galba is at that moment marching on the city, intent on replacing Nero, and hails him as new Emperor of Rome.