Lucius Sergius Catilina, B.C. 64, conspired with a large number of dissolute young nobles to plunder the Roman treasury, extirpate the senate, and fire the capitol. Cicero, who was consul, got full information of the plot, and delivered his first Oration against Catiline November 8th, 63, whereupon Catiline quitted Rome. Next day Cicero delivered his second Oration, and several of the conspirators were arrested. On December 4th Cicero made his third Oration, respecting what punishment should be accorded to the conspirators. And on December 5th, after his fourth Oration, sentence of death was passed. Catiline tried to escape into Gaul, but, being intercepted, he was slain fighting, B.C. 64.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Catiline's Conspiracy from Fact Monster: