Caesar winters his army in Gaul near the Italian border while his enemies in Rome fear that he will do something no Roman General has done: cross the Rubicon with his army. To counter-balance his opponents, Caesar puts his friend Mark Antony up for office as the people's Consul. Vorenus and Pullo accompany Mark Antony and Octavian to Rome. For Pullo, it's an opportunity to get drunk and ravish every woman in sight. He also loses all of his money in a crooked dice game leading to a major brawl. For Vorenus, he will have a reunion with his wife Niobe who he has not seen for 8 years. He's told that the baby he finds in his home is his grandson but Niobe is hiding a secret. In the Senate, there is a move to have Caesar declared a traitor but when Mark Antony tries to return to the Senate to veto their decision, Pullo is attacked by someone he fought the night before. Antony thinks the attack is against him and Pullo kills the man and Caesar declares Pullo a hero.

With Caesar quickly advancing toward Rome, Pompey begins ordering a retreat and forces his citizens to pick sides. Timon does Atia's dirty work and Vorenus cannot understand why no one is resisting while on a scouting mission.

Atia and her family have stayed behind when Pompey and others fled and she now throws a party for her triumphant uncle, Julius Caesar. She clearly has her sights set on the great leader and is puzzled when he sends her a guest list that includes Servilia of the Junii. She soon finds out why. Pompey wants to find out what happened to the gold from the Roman Treasury and sends his son Quintus to Rome to find out what happened. They go directly to Vorenus' home but he has no idea what they are talking about. Pullo arrives however and Vorenus tells him to go directly to Caesar himself and explain. Octavian meanwhile learns of one of his uncle's secrets.

Caesar contemplates Pompey's counteroffer. Vorenus continues to struggle as a businessman and must reevaluate his career choice. Atia schemes to come between Caesar and Servilia and Pullo seeks Octavian's help.

Caesar pursued Pompey to Greece but the tide has turned and it's Caesar who is on the run. He contacts Mark Antony, who he left in charge in Rome, to come and join him with the 13th Legion but Antony seems to be in no hurry. Vorenus has re-enlisted in Antony's Legion and he and Niobe have begun to renew their marital relationship. The presence of Niobe's sister is the only sour note in their house. Pullo meanwhile continues to train young Octavian in the use of arms and the boy's mother Atia is so pleased with his development that she decides he should take another step to manhood and orders Pullo to take him to a brothel so he can have his first sexual experience. Atia also continues with her scheming ways and believing that Caesar is done for, decides she had better make friends with Servilia.

Rejected by Vorenus and Eirene and racked by guilt for the killing of Eirene's fiancé out of a jealous rage, Pullo has sunk to working as an assassin for the gangster Erastes. When Pullo gets arrested for killing one of Caesar's popular opponents, he condemns himself by refusing to name who hired him, despite Octavian's attempts to defend him. Meanwhile, Vorenus finds his new official duties as magistrate tedious, especially when he gets caught between Caesar and the demands made by veterans' spokesman Mascias. Niobe revels in the prestige of Vorenus's office until Caesar invites the Voreni to a symposium at Atia's house. Despite Servilia's surreptitious propaganda depicting Brutus as a tyrant-killer, and the urgings of Cassius and his own doubts, Brutus resists turning against Caesar. Antony makes his move to win back Atia. On the point of death in a gladiator arena, Pullo finds a new reason to live that yet again puts Vorenus in a tight spot. Also, Caesar makes a move that compels the conflicted Brutus to make up his mind to turn against Caesar.

Vorenus' defense of Caesar lands him in an unexpected position of power within Rome. Meanwhile, Servilia hurls the final obstacle in her ambitious and complex revenge plan against Atia.

In the wake of Caesar's death, Mark Antony considers a move north, while Vorenus issues a curse he soon regrets.