Under the sinister influence of Sulla’s ghost, the reckless patrician Catiline organizes a conspiracy to overthrow the Roman Republic. The conspirators, among them the rash Cethegus and the outcast senators Lentulus and Curius, gather at Catiline’s home. Catiline and his wife pander to the weaknesses of each and skillfully manipulate them without allowing them to realize that they are puppets. The conspirators conclude their meeting with a gruesome sacrament and pledge their faith by drinking the blood of a murdered slave.

The first step in their plan is to have Catiline elected as one of the two consuls. Success seems probable after four of the candidates withdraw in favor of Catiline. That leaves only two competitors in the race: Antonius, impecunious and lukewarm, and Cicero, a new man but a dangerous antagonist. A Chorus of Roman citizens gathers and discusses the uncertainty of the survival of great national powers, which often seem to carry in themselves seeds of their destruction: Luxuries and vices soften nations and leave them easy prey to their own malcontents or to alien invaders.

Fulvia, the profligate wife of an elderly fool, numbers among her lovers the conspirator Curius and, on a very casual basis, Julius Caesar. As she is interested in wealth, not romance, she forbids her servants to admit the down-at-heels Curius on future visits. She is being readied for her social day when Sempronia visits her, a politician well past the bloom of youth. Sempronia is an eager supporter of the patrician Catiline and a scorner of “that talker, Cicero,” who presumes to be more learned and eloquent than the nobility. When Curius arrives to interrupt their gossip, Sempronia overrides Fulvia’s objections, ushers him in, and makes great play of leaving the lovers alone. Fulvia’s reception of Curius is so hostile that he becomes enraged and drops threats and hints of future greatness and power. Fulvia immediately shifts to the tactics of Delilah and wheedles information about the conspiracy from him.

The Chorus gathers before the election and prays for wisdom to choose consuls worthy of Rome’s great past. Antonius and Cicero win the election, which shocks and infuriates Catiline and his party. Cato praises Cicero warmly, but Caesar and other sympathizers of Catiline regard the new consul with veiled hostility or open contempt. Catiline masks his fury in public, but in private he plans rebellion and civil war. Fulvia, partly because of self-interest and partly because of a vain dislike of playing second fiddle to Sempronia, carries information about the conspiracy to Cicero. He uses it to intimidate Curius, appealing to his greed and winning him as a spy. Fulvia serves the same purpose among the women conspirators. Alone, Cicero bemoans the low estate of Rome, which is reduced to dependence on such tools as Fulvia and Curius for safety. He strengthens his position still further by giving a province to Antonius.

Caesar shows Catiline favor and gives him advice, but he does not join the assemblage of conspirators. At the conspirators’ next meeting, plans are laid for setting fire to the city at strategic points and starting local uprisings to be timed with an invasion from outside. The first move is to be the murder of Cicero that very night. The women conspirators enter with Catiline’s wife, Aurelia. Under cover of their excited chatter, Curius whispers to Fulvia the plan to assassinate Cicero. She leaves the meeting and warns Cicero in time for him to gather protecting friends and impartial witnesses. Although the attempt on Cicero’s life fails, the threat of civil violence terrifies senators and citizens. The Chorus expresses horror...