The episode opens with a brief exposition, explaining the political situation in Rome: for 400 years since the expulsion of the Monarchs, Rome has been a republic, but tensions between the Patrician and Plebian classes have mounted steadily. Order is maintained by a sharing of power between two men, Julius Caesar, and Gnaeus Pompeius Magnus. Pompey was once acknowledged by all to be the greater man, but Caesar's eight-year Gallic Wars have made him increasingly rich and popular. Caesar's growing popular support causes the Patricians to grow more and more fearful. With his patrician pedigree, and his enormous army, wealth, and popular support, Caesar might make himself king.
The scene opens in 52 BC, during the Siege of Alesia. In the front lines of the 13th Legion, Centurion Lucius Vorenus commands his men as Gallic warriors fall on his line. In contrast to the Gauls' chaotic charge, the Roman files fight with machine-like precision â until one Legionary, Titus Pullo, breaks ranks and wades into the crowd of Gauls, hacking them down. Vorenus angrily orders him back into formation, and then orders a small detachment to follow him to rescue the surrounded Pullo. A drunken Pullo is not appreciative of the efforts of his comrades, and floors Vorenus with a right hook before being knocked to the ground and dragged back into the lines by the other legionaries.
In the encampment of the 13th Legion, the assembled soldiers watch as Pullo is flogged, and condemned to death for striking an officer, despite his valorous service record. An amused Mark Antony looks on.
The day after the siege, Vercingetorix, "King of all the Gauls," is brought before Caesar, stripped, forced to kneel, and made to kiss the Aquila of the 13th Legion. The eight years of the Gallic Wars are over. But later, as the slave traders divvy up the captives, a message comes from Pompey in Rome, informing Caesar that Julia, Caesar's daughter and Pompey's latest wife, has died in childbirth. Pompey is genuinely heartbroken, but Caesar is pensive, knowing that Julia's death has severed the last real connection of loyalty between himself and Pompey.
In Rome, several representatives of the aristocratic party â Cato the Younger and Scipio among them â watch with scorn as Caesar's representative scatters largesse to the people. Elsewhere, a hireling named Timon delivers a prize white stallion to Caesar's niece, Atia of the Julii and, in what appears to be a customary arrangement, takes his payment by having sex with her. Atia informs her son, Octavian, that she plans to make Caesar a gift of the horse, and to ensure that he remembers them above all other well-wishers, orders Octavian to deliver the horse straight to Caesar in Gaul.
In the Roman Senate, Cato moves that Caesar be stripped of his command and recalled to Rome to answer charges of misusing his office and illegal warmongering. Pompey, as sole Consul, vetoes the motion, insisting that Caesar is his friend. Cicero, attempting to straddle the fence, decries Cato as too extreme, but equally decries Pompey as too conciliatory. The attempt does not go over well, and both sides ridicule him. At the theatre that night, Scipio introduces his daughter Cornelia Metella to Pompey as a prospective new bride, while Cato warns him that he must ally with the Patricians against Caesar before it is too late: however,Pompey publicly asserts again he believes Caesar, as his friend, means no harm.
Privately however, Pompey is troubled and vexed by Caesar's rising prestige and power. He is especially irked when he learns that the prize white stallion, which he wanted to buy himself, has already been bought by Atia. He tells one of his slaves to "kill two birds with one stone" during a planned trip to Gaul.
At night in the encampment of the 13th Legion, the Aquila is stolen by brigands. To avoid a potentially disastrous drop in morale, Antony orders Vorenus to retrieve it. On Vorenus's orders, captives from each tribe in Gaul are crucified until one of them reveals that the thieves were "Blue Spaniards" headed to a distant corner of Gaul. Feeling his mission to track them down is doomed to failure, Vorenus has the already-doomed Pullo released from the stockade to assist him.
In camp, Caesar welcomes Marcus Junius Brutus, a sort of unofficial stepson, since his mother is Caesar's lover, Servilia of the Junii. Once back in Rome, Servilia eagerly presses her son for news from Caesar. At a party thrown by her, Brutus confides to Pompey that the loss of the eagle has made Caesar unusually vulnerable â to hear Brutus tell it, his men are on the brink of mutiny, and Caesar himself is demoralized.
On the road to Caesar's camp in Gaul, Octavian's party is ambushed by thugs, who massacre everyone else in the party and take Octavian and the prize horse captive.
Caesar writes to Atia, instructing her to find a suitable female from their family to replace Julia as Pompey's wife. In short order, Atia instructs her daughter, Octavia to divorce her husband, Glabius, despite Octavia's protests that they are deeply in love with each other. Atia then presents Octavia to Pompey at a party, and even offers her for pre-marital relations, an offer Pompey takes advantage of.
Vorenus and Pullo set off in search of the eagle. But Pullo falls asleep while on watch and their horses are stolen from them during the night. Grumbling and hiking horseless through the woods, the pair encounter the pack of thugs with Octavian and the stolen horse and kill them all.
When Vorenus explains who they are, Octavian shows himself to be much more shrewd and devious than either he or Pullo. He explains that their mission is only a gesture, since the theft of the eagle is actually a blessing in disguise to Caesar: now that Julia is dead, civil war between Caesar and Pompey is inevitable, but Caesar needs Pompey to make the first move so as not to appear the aggressor; now Pompey is likely to do just that if he believes that Caesar's soldiers are on the verge of deserting him.
But no sooner has Octavian said that Caesar would prefer the eagle to remain lost, that Vorenus and Pullo find a vessel of blue skin dye in the thugs' cart, along with Pompey's slave, who dies clutching the stolen eagle in his hands as he tries to make a run for it.
The trio returns in triumph to camp, where a surprised yet grateful Caesar takes stock. He has the eagle back, but more than adequate proof of Pompey's hostility. He sends the head of Pompey's slave back to its master and informs Pompey of his next move: to winter the 13th Legion at Ravenna, on the border with Italy, in preparation for pressing his rights to the Consulship.
Pompey breaks off all ties with Caesar and takes Cornelia as his wife. Octavia, humiliated at being used by Pompey and heartbroken over her now-pointless divorce, says she wants him dead. Atia, if anything, seems pleased that her daughter has developed a taste for other men's blood.