As the wars in Gaul come to an end, Caesar is faced with both triumph and tribulation. In Rome, Pompey must balance honour and politics as he's urged to carry out an act of betrayal. Atia of the Julii tries to steer her family between the growing divisions of power.

Anointed People's Tribune by Caesar, Mark Antony returns to Rome with Octavian's liberators, Vorenus and Pullo. After the Senate rebuffs Caesar's compromise for a heroic return to Rome, Antony learns that Pompey has drafted an ultimatum stripping the general of his powe

Caesar is making his way towards Rome, though Vorenus is considering why the army's encountered so little resistance during their patrols. In Rome, Pompey orders a retreat of his forces and assigns his best men to take the city's treasury to their planned destination.

As Pompey 'manoeuvres' outside the city, Caesar seeks to strengthen his hold on Rome. Atia throws Caesar a welcome home party. Pullo delivers Quintus Pompey to Caesar, who in turn returns Quintus to his father with an offer of a truce he knows Pompey will never accept.

Caesar weighs Pompey's counteroffer against Antony's recommendation to chase down Pompey's vulnerable army. Vorenus is forced to reconsider his career choices after a series of business setbacks. A jealous Atia concocts a clever scheme to separate Caesar from Servilia.

Antony is running Rome while Caesar pursues Pompey in the East, but news that the tide has turned, and that Pompey now pursues Caesar, leaves Antony deciding whether to remain loyal or turn against Caesar as Atia and Pompey wish. Atia tries to mend fences with Servilia.

Marooned in the Adriatic Sea, Vorenus and Pullo look to survive. In Greece, Pompey decides to attack Caesar's depleted forces whose lack of options turns into their greatest strength. In Rome, Octavia is enlisted by Atia to ask another favour of Servilia.

Having pursued Pompey into Egypt, Caesar meets Ptolemy XIII who offers the general a surprise gift. Vorenus & Pullo free Ptolemy's incarcerated sister, Cleopatra. Caesar seeks payment from Egypt for past debts and ends up forging a strategic union to ensure his legacy.

With Scipio and Cato defeated, Caesar returns home to a hero's welcome. Vorenus and Pullo's showdown with local thug Erastes gets an unexpected reprieve from Caesar. Servilia's plan to use Octavia to unearth a secret about Caesar backfires.

Proclaimed Emperor by the Senate, Caesar declares the war over. No longer a soldier, Pullo eyes a pastoral future with Eirene; Vorenus runs for municipal magistrate; Octavian retrieves Octavia from her self-imposed exile; Servilia invites Quintus Pompey into her home.

While Pullo descends into Erastes' netherworld, Vorenus negotiates a severance for veteran soldiers on behalf of Ceasar, who invites him and Niobe to one of Atia's parties. Cassius tries to convince Brutus that the life and death of the Republic is indeed in his hands.

Pullo and Vorenus are now heroes to the Roman rank and file, causing Caesar to reward those he would have punished. To the chagrin of the old guard, Caesar decides to add some new faces to the Senate. Servilia conquers the final hurdle in her ambitious revenge scenario.