In this programme, Mary descends into the city streets to discover the dirt, crime, sex and slum conditions in the world's first high-rise city. This Rome is not the marble Rome we know, but a vast, messy metropolis with little urban planning, where most Romans lived in high-rise apartment blocks with little space, light, or even sanitation. Forced outdoors into the city streets, she reveals where they went to hang out, get drunk, have sex and get clean. She looks at the Forum as a place of gamblers, dentists and thieves, and she explores the lustiness of Roman bar life and jokes. Finally, exploring law and order from the bottom up, Mary examines how this city really worked. She meets Ancarenus Nothus, an apartment dweller who lived in fear of the rent collector; Notorious Primus, who wrote about his three great pleasures in life - baths, wine and sex; and Unlucky Doris, a seven-year-old girl killed in one of Rome's many fires.

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 19 Legions strong.

With the defeat of the Egyptian fleet at Actium, Mark Antony and Cleopatra retreat to their palace and await their fate. Believing that Cleopatra has taken her life, Mark Antony decides follow her into the afterlife. She has other plans however and is quite prepared to negotiate with Octavian if there is any possibility her life and those of her children will be spared. Cleopatra asks Vorenus to take her son Caesarian to safety and Octavian sends Pullo after them. The old friends are soon together again.

Millions of tourists photograph the ancient monuments of Rome every year. But is there more to them than people guess? There's new evidence that these ruins were once machines, designed by Rome's emperors to connect their power with the sun. Did Roman emperors harness the power of the universe to awe and terrify the people of Rome? We uncover the last, great mysteries of the ancient world's greatest empire.

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.'

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.