Act III Scene i
The Senators, with Coriolanus, are on their way to the Capitol. Titus Lartius tells Coriolanus that Aufidius quickly rearmed after his defeat, and so Rome swiftly made a peace treaty.
Coriolanus's party is stopped by Sicinius and Brutus. The tribunes tell them that the plebeians have changed their minds and that it is dangerous for them to proceed. Coriolanus immediately suspects a plot by the tribunes, but the tribunes insist that the change comes from the plebeians themselves, who are angry that Coriolanus mocked them.
Coriolanus furiously insults the plebeians. He warns his fellow patricians not to pander to them, as this will foster rebellion. He says that the patricians and the plebeians cannot both have power, as the plebeians are in the majority. If both try to hold power, confusion will result, and one will destroy the other. Because of the plebeians?cowardice in battle, Coriolanus despises them and believes that they do not deserve a civic voice. Menenius tries to silence him, but Coriolanus continues to denounce the chaos and instability of a society that is governed by the rabble. Brutus and Sicinius accuse him of treason, and order an Aedile (a policeman answerable to the tribunes) and a crowd of plebeians to arrest him.
The tribunes, without a trial, sentence Coriolanus to death by being thrown off the Tarpeian rock, a cliff-face in Rome from which criminals were thrown to their deaths. Coriolanus draws his sword. Menenius calls upon the patricians to help Coriolanus, and they all beat off the tribunes and plebeians. Coriolanus wants to stand and fight, but Menenius and the patricians insist that he go home and leave them to smooth things over with the plebeians. Coriolanus leaves.
Brutus and Sicinius reappear with a crowd of plebeians, who are ready to seize Coriolanus at his home and throw him off the Tarpeian rock. Menenius verbally defends Coriolanus while adopting a conciliatory attitude to the plebeians. He at last persuades the plebeians to try Coriolanus by proper legal process, to avoid civil war. The tribunes arrange to meet Menenius and Coriolanus in the market place.
This turbulent scene marks the turnaround in Coriolanus's fortunes. As he is on his way to the Senate to be proclaimed consul, he is stopped by the tribunes, who have worked the mob up into anger over his pride and contempt for them. Just as the tribunes predicted and hoped, Coriolanus is unable to deal calmly with the news that the plebeians have withdrawn their support. His true attitude to them, which he had managed to keep under control in the previous scene, erupts, and he unleashes a stream of contempt at them. He calls the plebeians "Hydra?(III.i.93), a reference to a mythical poisonous water snake with many heads. According to legend, if one of the Hydra's heads were cut off, another or several would grow in its place. The image implies something unnatural, monstrous, and ungovernable.
In spite of the play's ambivalences towards both plebeians and patricians, what is not disputed, but presented as a self-evident truth by Shakespeare, is Coriolanus's view that having two authorities (rulers and people) in a state results in chaos and destruction. He says, "my soul aches / To know, when two authorities are up, / Neither supreme, how soon confusion / May enter 'twixt the gap of both, and take / The one by th'other?(III.i.108-111).
Coriolanus shows his unsuitedness to the political role when he draws his sword against the tribunes and their supporters. He feels at home in the role of warrior and wants to fight out his dispute with the plebeians. It takes all the political skills of Menenius and the other patricians to persuade him to leave the scene. Cominius points out that now is not the time for Coriolanus's warrior methods: "But now 'tis odds beyond arithmetic, / And manhood is called foolery when it stands / Against a falling fabric?(III.i.244-246). The sense is that Coriolanus's time of glory passed with the end of the war. In a time of peace, different skills are required. But Titus Lartius's warning at the opening of the scene that Aufidius has rearmed suggests that in the future, Coriolanus's warrior skills will once again come into their own. His drawing his sword against the representatives of the Roman people asks the question: who will be his enemy next time ?Aufidius, or the people of Rome? Suspense is created, to be resolved in future scenes of the play.