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. 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. Pompey knows that they need only wait, and starvation and weariness will cause Caesar's troops to desert. However, as predicted by Caesar, the politicians in the camp, led by Cato the Younger, want a decisive victory and pressure Pompey to attack. Cato and Scipio urge Pompey to crush Caesar in a final battle, reminding him of his reputation as a war hero. Pompey eventually gives in and agrees to attack Caesar.
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 resolve to retreat to Africa and continue the war from there, although Brutus wearily remarks that they are "running out of continents" to flee to. Sick of fighting and the constant retreats, Cicero and Brutus both declare their intentions to surrender to Caesar and beg for his mercy. "I'm not afraid to die," Cicero declares in response to a sympathetic Scipio's comment they will probably be executed, "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. Caesar is also overjoyed by their news that Pompey has survived Pharsalus, though disheartened to learn his old friend turned bitter enemy has no intention of surrendering.
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. Caesar is furious that Vorenus let Pompey go, but surprises Antony by letting Vorenus off with only a reprimand. When Antony argues Vorenus should be executed for such an error, Caesar explains that he believes Vorenus and Pullo are being protected by powerful gods, having recovered his missing Eagle in Gaul, stumbled upon a wagon full of treasury gold, survived a shipwreck that drowned the rest of their legion, and then found Pompey on a beach. He will not kill men "with friends of that sort."
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.This episode features the Battle of Pharsalus, which was a decisive battle of Caesar's Civil War.
On the beach, Septimius jokes with Pompey about needing to "earn one's salt." This modern expression originated with the Romans (according to Pliny the Elder), salt was actually used as a form of currency used to pay soldiers. In fact, the word "salary," is derived from the Latin word salarium, which in turn is derived from the Latin word for salt.
The last scene is based on Plutarch's Life of Pompey, which stated that Pompey was ambushed on the beach at Alexandria by members of the Egyptian King's bodyguard, including former centurion Lucius Septimius.