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.

As they prepare their counterattack against Caesar, Pompey's Republicans begin to squabble over both the anticipated spoils and the method of finishing Caesar off. Badly outnumbered, Caesar and Antony make their stand at Pharsalus. As they try to reach Caesar in Greece, the shipwrecked Vorenus and Pullo confront an unexpected dilemma.
Back in Rome, Atia again sends Octavia to beg protection from Servilia, who complies readily to encourage her growing friendship with Octavia. Niobe's sister Lyde comes back to see her and comforts her over Vorenus's disappearance.

In Egypt, Caesar rebukes the advisers of the boy king, Ptolemy XIII, for their presumption in eliminating Pompey and demands the man who killed him. Caesar decides to intervene in the dispute between Ptolemy and his sister-wife, Cleopatra, to ensure both Rome's grain supply and his own access to Egypt's treasure.
Antony, in an unusual show of prudence, advises against this with only half a legion in Alexandria and Cato and Scipio still at large in Africa. In Rome, Brutus gets a chilly reception from Servilia when he returns home from Greece.

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.

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

Caesar has been murdered, Mark Antony emerges from the Senate in shock, only to face Quintus Pompey and his thugs, who immediately follow him to try to kill him. Brutus returns home shaking after the murder. His mother is already plotting the return of the Roman Republic. Titus Pullo asks Eirene to marry him and she accepts. Erastes Fulmen kidnaps Lucius Vorenus' children and sister-in-law.
Mark Antony proposes an amnesty to the rest of the senate to keep the peace and allow the Republic to continue. Vorenus says goodbye to Niobe while Rome says goodbye to Caesar. Vorenus and Pullo track down Fulmen to a bath house, where he tells them he killed Vorenus' family.