Lucius Vorenus and Titus Pullo wash ashore on a small cay, after their ship is lost at sea. Without water, food, or any sign of rescue, they are nearly resigned to their deaths, when Vorenus notices the corpses of their dead comrades floating, and the two men fashion a raft using several bodies to float it, and paddle out to sea.
In Julius Caesar's camp, Mark Antony and a small contingent of soldiers have arrived, but the majority of the 13th Legion has been lost at sea. Pompey's army has Caesar pinned down, and outnumbers his forces 3 to 1. Grimly, Caesar and Antony decide they have no choice but to make what will probably be their last stand from where they are.
In Pompey's camp, his officers consider the war all but over, but Cato the Younger is surprised to hear that Pompey does not plan to engage Caesar. All they need do, he explains, is keep Caesar boxed up for another few weeks, and starvation will cause his troops to desert him. Cato and Scipio urge Pompey to crush Caesar in a final battle, reminding him of his reputation as a war hero. Pompey reluctantly agrees.
In the ensuing battle, Caesar's forces inflict a devastating defeat on Pompey. Caesar, exhausted, staggers back into his tent and instructs Posca to send word of his victory to Rome, before collapsing.
In Pompey's camp, Cato and Scipio declare that they must retreat to Africa and gather new forces. Sick of fighting and the constant retreats, Cicero and Marcus Junius Brutus both declare their intentions to surrender to Caesar and beg for his mercy. "I'm not afraid to die," Cicero declares, "I'm tired, and I want to go home."
After they have left, Pompey consults with Scipio and Cato, and the three decide not to travel together. While the former make their way to Africa, Pompey makes his way with his wife and children to Amphipolis, posing as a traveling merchant.
In Caesar's camp, Cicero and Brutus are welcomed back with open arms by an ebullient Caesar. Befuddled, they remind him they are enemy combatants, but he will have none of it: "We are old friends, who have merely quarrelled." He invites them to share the table with the rest of his staff, who are busy celebrating the victory.
When they reach the coast, Pompey's children come across Vorenus and Pullo washed ashore. Pullo and Vorenus recognize Pompey, though they conceal it. Pompey's party takes them in and gives them shelter and food.
Out of Pompey's earshot, the leader of his escort tries to recruit Vorenus and Pullo to help overpower Pompey's guards and take the family prisoner, promising a share of the rich reward Caesar will no doubt offer. Pullo is all for the suggestion, but Vorenus rejects it as dishonorable. The guide tries to ambush Vorenus, and Vorenus stabs him through the throat, alerting Pompey. Vorenus informs Pompey that he and his family are now officially prisoners of the 13th Legion.
In private, Pompey admits to Vorenus who he is. He tells an interested Vorenus how he was defeated at Pharsalus, then tearfully pleads that his family be allowed to make their way to freedom. Taking pity on the old man, Vorenus lets his party go, over Pullo's objections.
Pullo and Vorenus make their way back to Caesar's camp and explain what happened. Caesar and Antony are both furious that Vorenus let Pompey go, but Caesar surprises Antony by letting Vorenus off with only a reprimand. In private, when Antony points out Vorenus's actions are cause enough to execute him, Caesar says Antony that Vorenus and Pullo have powerful gods on their side: they found Caesar's stolen Eagle in Gaul; Pullo stumbled onto a wagon full of treasury gold; the two men survived a shipwreck that claimed the rest of their Legion, and then found Pompey Magnus on a beach. Caesar hesitates to kill any man with such friends.
In Rome, at Atia's urging and Servilia's invitation, Octavia has continued to visit Servilia's house. At first, Octavia is the supplicant, begging on her mother's behalf for help in keeping their house safe when the news of Caesar's defeat reaches Rome. But their positions are abruptly reversed when the news arrives that Caesar has triumphed, and Brutus's whereabouts are unknown. Servilia collapses with tears. Octavia comforts her, and then kisses her. The two women are later shown lying in bed together.
Pompey's party makes its way from Amphipoli to Alexandria in Egypt, confident of a warm welcome from the reigning king, Ptolemy XIII. While Cornelia and his children watch from their boat, Pompey is rowed ashore, where he is greeted by an ex-comrade from Spain, Lucius Septimius, now serving as a mercenary in the Egyptian army. Pompey reaches out to shake Septimius's hand, but Septimius seizes his arm and stabs him in the chest, sadly stating he is acting under orders. While Cornelia shields the children's eyes, she watches in horror as Septimius beheads Pompey and lets his corpse topple into the water.