52 B.C. Eager to return to Rome after eight long years of war, Gaius Julius Caesar ends his campaign with a big triumph in Gaul--and news of a shattering personal loss at home. When his army's gold standard is stolen, Caesar's cousin and commander Mark Antony enlists two soldiers, Centurion Lucius Vorenus and Legionnaire Titus Pullo, to track it down.

Appointed People's Tribune by Caesar, Mark Antony returns to Rome with Octavian's liberators, Vorenus and Pullo. After being feted by a grateful Atia, Vorenus heads home to his family for the first time in eight years, while Pullo heads for the brothels. Shocked to see a husband she thought was dead, Vorenus's wife, Niobe, presents him with a family he barely recognizes. 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 power. With tempers on both sides reaching a boiling point, unfinished business involving Pullo spawns a Forum melee that all but ensures an unhappy outcome in the Pompey-Caesar standoff--and sends Pullo and an injured Vorenus back into Caesar's ranks.

Scouting for Caesar some 30 miles from Rome, Pullo, Vorenus and some Ubian soldiers meet minimal resistance from a green group of Pompey's recruits. Alarmed at the speed with which Caesar's army has advanced, and with a less-than-full complement of soldiers at his disposal, Pompey makes an unusual tactical decision: abandon Rome to Caesar, at least temporarily. The order forces patrician families to choose sides--while Servilia, Caesar's longtime lover, decides to stay in Rome, her son, Marcus Junius Brutus, flees the city with others faithful to Pompey. After seeing her family's fortunes fall and rise in the course of a few hours, Atia enlists her mercenary, Timon, to ensure her family's security and eliminate her daughter's Pompeiian husband, Glabius. As Vorenus marvels that Rome has been left undefended, Pullo sees his uncanny good fortune continue after his unit intercepts a cargo wagon on the city's outskirts.

As Pompey 'maneuvers,' Caesar seeks to consolidate his hold on Rome. Atia throws a party to welcome Caesar home, while Vorenus throws one of his own to usher in his new life. Pullo's run of luck continues when he delivers Quintus Pompey to Caesar, who in turn returns Quintus to his father's camp--with an offer 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 leave him with little income to support his family. A jealous Atia concocts a clever scheme to separate Caesar from Servilia. Pullo is recruited to tutor Octavian in the art of soldiering, but ends up learning a lesson or two from the boy.

Mark Antony is running Rome while Caesar pursues Pompey, but when news comes that the tide has turned and that Pompey now pursues Caesar, Antony must decide whether to stick by his old commander or turn against him. Pullo takes Octavian to a brothel; Atia attempts to mend fences with Servilia; and Vorenus and Niobe rediscover their intimacy, albeit briefly.