There were various events in the Roman Republic that led to its fall and the rise of the new system of government dominated by a single man, the emperor. One such event was the rebellion of Lucius Sergius Catilina (Catiline) who had earlier been accused of adultery with a Vestal Virgin, which was a serious crime whose punishment could include burying the woman alive.
When Catiline discovered he couldn't become consul -- a position that would have made him safe from his debtors for the year in office and then the next year when he would have been sent off to take charge of and milk (another) province -- he got together with a bunch of other unhappy Romans to form a conspiracy to take over Rome. His plot was discovered prematurely.

Cicero, who was consul, and had additionally been given the ultimate senate power in order to take charge of a dangerous situation, delivered speeches against Catiline and his fellow conspirators that are known as Catilinarians. Cicero argued with the other senators that the conspirators should be executed. Some, like Caesar, had more moderate proposals, but Cicero prevailed. Since he was the consul, when the Romans later decided execution was excessive, Cicero was blamed. Cicero wound up in exile; Catiline, eventually, dead.

On November 9, 63 B.C. Cicero delivered his 2d Oration against Catiline.

• Read more about the Catilinarian Conspiracy.

Catiline Sits Apart in the Senate image © Clipart.com