Lucius Vorenus, the power-hungry "Son of Hades", controls the Aventine but practices a pointless, beastly reign of terror, coming down hard on gang captains for futilities, and nearly ruins his friendship with Pullo, whose efforts to calm things down are mistaken for disrespect and disobedience, even starts a fight once he learns the truth about Niobe; Pullio leaves Rome disgusted. After Atia convinces Marc Antony the governorship of ghastly Macedonia after his consulate would not only be unpleasant but leave him exposed to his dangerous enemies, he puts the heat on senatorial leader Cicero to give him Gaul instead, which once was the base for Julius Caesar's coup d'état. The slave Duro endures male prostitution but most arrogantly demands extra pay and even a kiss from Servilia as it will take more time to commit the planned murder in Atia's home. Marc promises Atia not to hurt Octavian, whose recruiting he calls a joke, after putting down his party's expected plot. Brutus has a hard time controlling himself while soliciting the Bithynian king's financial support to raise an army. Instead of proposing Antony for governor of Gaul, Cicero sends an extremely insulting speech and joins Octavian's growing army.

Having learned that Vorenus' children are alive, Pullo sets off to find him in Gaul where he is again a serving soldier in Mark Antony's army. He had hoped to arrive before Octavian and Antony's armies meet in battle. Too late however, he is forced to find what is left of Antony's army in the mountains. He finds Vorenus alive and well, if somewhat battle worn, and they set off to find the children. The victorious Octavian plans his return to Rome. In Western Turkey, Brutus and Cassius amass their own army, now 9 Legions strong. In Rome, Servilia's attempt to kill Atia fails and Atia has her kidnapped tortured beyond what even her henchman Timon can stand.

Vorenus and Pullo return to the Collegium in Rome with Vorenus' family, but some of the "changes" that Pullo had warned him about regarding his two daughters Vorena both the Elder and Younger, as well as his wife's son, begin to manifest themselves into hostility and resentment. But Vorenus is completely oblivious to this, and is too blissfully happy to return to the role of 'father'. Meanwhile, Octavian finally returns and manages to negotiate the Senate Consul's seat from a scheming Cicero, but in spite of his promise to 'faithfully follow' the older man's counsel, Octavian proves that he certainly has a mind of his own, vowing to hunt down and kill the assassins of Julius Caesar, much to Cicero's consternation. Elsewhere, Brutus and Cassius receive news that might prove useful in staging a triumphant return to Rome, as well as the ultimate defeat of both Mark Antony and Octavian's forces. Also, Atia has a reunion with her son that is strained to say the least, but there is a tentative reconciliation between them. And another, much less stressful reunion between two lovers, Octavia and Agrippa, who saves her from an attempted date-rape at an orgy party, will bring about an unforeseen alliance between two formerly mortal enemies.

Cicero is finally undone by his duplicity in the form of Titus Pullo, acting upon Octavian's request to assassinate all supporters of Brutus in Rome. Pullo and Vorenus enjoy a happy if counterfeit outing with their families in the countryside to hide their assassin mission. Vorena the Elder's dangerous dalliance with one of Mimeo's men continues, and the torrid affair between Octavia and Agrippa escalates. Atia's casual cruelty to ask for the assassination of people she doesn't like results in complete disaster for Octavia's friend Jocasta. Elsewhere, the headstrong Levi engages Timon in a plan to assassinate King Herod by recruiting in the synagogue where they worship. Disastrously out manned, Brutus and Cassius engage the combined legions of Mark Antony and Octavian, and confront their fates in the ferocious battle at Philippi.

Inconsolable at the death of Brutus at Philippi, Servilia makes her final bid to gain the ultimate vengeance against Atia. Meanwhile, Eirene and Gaia have a major falling-out, prompting Eirene to demand that Pullo properly chastise the slave. When he does, the dynamic between the two of them changes in a violent and unexpected fashion. King Herod engages Mark Antony as a reluctant ally by offering a generous gift of 20,000 pounds of gold, and when Posca is excluded from sharing in the windfall, he engineers a move behind-the-scenes that will once again strain the uneasy truce between Octavian and Antony. Vorenus eldest daughter, Vorena, is blackmailed by Mascius into spying on her father after her tryst with one of his men is discovered. The end of two love affairs and a marriage in the house of Julii have major ramifications for life in the city and on the Aventine when Octavian insists on the courtship between Octavia and Mark Antony which irks both Atia and Agrippa. Also, a desperate move to assassinate Herod finishes the relationship between contentious siblings Timon and Levi when they have a falling out, and Levi gets killed by accident.

Octavian takes a new bride, Livia, and then introduces her to his family in a startling way... by having her witness the punishment he metes out to Atia and Octavia, for secretly defying the social constraints established through the facade of Octavia's "marriage" to Mark Antony. The vengeful Gaia carries out her plan to poison Eirene, which produces most dire consequences for Pullo, and no one else is the wiser. Meanwhile, Octavian, Antony, Maecenas, and their associates barely maintain their relationships of congenial contempt and hypocrisy, as everyone tries to figure out who has duped whom with the disappearance of the gold that was Herod's 'gift.' Now forced by Octavian to leave Rome to serve as an 'ambassador' to Egypt, Antony defies the conditions of Atia's house arrest to bid her a bittersweet farewell. The same can be said of Agrippa, who learns some startling news as he severs his relationship with Octavia. Timon also decides to move with his family to Judia to start a new life over for themselves. With the theft of the gold, Lucius and Pullo suspect and accuse a badly-wounded Mascius of having engineered a double-cross, but the real traitor of Vorenus' gang comes to shocking light which is the eldest Vorena. Now having pinpointed Memmio as the real culprit, Pullo takes the group to meet for a parlay with the devious captain and his cohorts, resulting in swift and bloody retribution for the traitors. A despondent Vorenus, his family fractured once again, begs Antony to allow him to come to Egypt, and finds his offer grudgingly accepted. Antony returns to Egypt and is reunited with the seductive Cleopatra.

Seven years have passed since Antony's departure from Rome, and the former commander, dissipated and debauched - held in thrall by the charms and sexual prowess of his new bride, Cleopatra, withholds precious shipments of grain from Rome, where people die in the streets from hunger. Unable to incite a war with Antony and Egypt without committing political suicide, Octavian sends Atia and Octavia to Alexandria to mediate and reason with Antony; a strategy which proves predictably unsuccessful. However, former Roman senator Posca and his wife, Jocasta, flee Alexandria with Atia and Octavia to Rome where he provides Octavian with all the ammunition he needs to bring about a war with Antony and Cleopatra. Meanwhile, Pullo has taken over the Avantine gangs of Rome. But later, a fatal blow is stricken to the torrid affair that has continued between Pullo and Gaia, as karmic debt comes to call when she saves him from the sadistic Memmino, but gets fatally wounded, and she lets it slip to Pullo that she was the one who poisoned Eirene. Octavian asks Pullo to join him in the campaign against Egypt, and Pullo agrees without question, hoping to reunite and redeem his blood brother, Vorenus, who continues to stand by Antony's side despite his growing contempt for his commander. Octavian calls for war against Antony in the Senate, and is met with thunderous approval.