Coriolanus is an aristocratic snob who hates the lower classes and thinks they shouldn't have any say in political matters because they're idiots and cowards. Problem is, he needs their votes when he returns from war and runs for political office. His mom and buddies convince him to kiss up to the voters, even though he hates them.
Uh, oh. Coriolanus just can't keep his mouth shut. While campaigning, he manages to insult the Citizens and their tribunes, which gets him exiled from Rome and accused of treason. Coriolanus is seriously ticked off so, he joins his former enemies (the Volscians), raises a giant army, and marches towards Rome. Just before he's about to demolish the city, his family begs him for mercy and gets him to agree to a peace treaty.
Coriolanus has made nice with Rome, but he's still not happy with them. He heads back to the Volscians, but before he can explain why he went marshmallow soft on Rome, he's accused of treason against the Volscians and is killed.