After a month of indolence in Nero's Rome, the TARDIS team find themselves drawn to the Empire's Capital. The cliffhanger (literally, the TARDIS was hanging on the edge of a cliff at the end of The Rescue) is re-shown, and we find the travelers in unexplained (until later) comfort. With Barbara and Ian rather flintily comfortable with each other, I might add.
If we begin discussing the story collectively known as The Romans by looking at the character of the Doctor, we can see what a difference a year and the first change of companion makes. Hartnell is clearly having a whale of a time in this, the first comedy historical, scripted by Dennis Spooner. Hartnell's Doctor is buoyant throughout this episode, preening himself for being two steps ahead of everyone--and generally being right about the fact. It's a great performance; even his line flubs aren't bothering him anymore (in season 1, he seems visibly frustrated whenever he blows a line). This is Hartnell in full command of his performance and his show. The fact that this makes his Doctor more amusing and yet more pugnacious--well, all those tough guy roles Hartnell played before the Doctor left a mark.
Maureen O'Brien as Vicki is enjoying the whole thing, too--she's bubbling with laughter through most of the story, and generally enjoying being paired with the eponymous character for most of the story. O'Brien is like a partner-in-crime for Hartnell--and in fact, as O'Brien described their relationship, "“We had fun. Our rehearsals were fun, despite when he broke into spitting, snarling rages. He had a laugh, he liked to work. He liked his whisky. We had a good time.” In an earlier interview, she was quoted as saying her "job really, since the acting was no sweat, was to laugh Bill out of his rages and tantrums, which I did thoroughly, and enjoyed! He’d get very tetchy, but that was just Bill’s personality, that’s how he was." That shows even in this early episode.
Those who contend that Barbara and Ian end up as a couple could rest their case on this story alone. The chemistry between Jacqueline Hill and William Russell is dead on. In first part, their banter has a lovely, teasing, unselfconscious feel to it:
BARBARA: You know Ian, I could get used to this sort of life.Grand as it is to see them all enjoying themselves, the plot requires them to leave the villa. So the Doctor and Vicki wander off to Rome, where he is mistaken for a politically-conspiring lutist, while Barbara and Ian are kidnapped and sold into slavery. These plots are pretty dark, at least to begin. Barbara's kindness to a sick fellow prisoner catches the eye of Tavius, Nero's steward, who buys her. Ian becomes a galley slave, and goes through a capsule version of Spartacus.
IAN: Mmm. I already have. What about another drink? [He's clearly asking her to get it]
BARBARA: Oh, yes, I'd love one. Thank you.
IAN [wryly smiles; gets up to get it]: No ice, I'm afraid.
BARBARA: There's some in the fridge.
(Ian starts to leave the room before the penny drops)
IAN: Very funny, very funny.
BARBARA: You went!
IAN: Well, here's to the first fridge.
IAN: O tempora, o mores.
Meanwhile, Barbara finds herself trapped in Carry On, Cleo, with six-time Carry On veteran Derek Francis playing a lust-addled Nero, who falls into what I would call Rule 2: Everybody wants Barbara. These scenes are of course very dated, but well within the Carry On tradition, or even A Funny Thing Happened on the Way to the Forum.
The Doctor, meanwhile, is beset by Nero (who wants to kill him for receiving more applause as a player than Nero has), Tavius (who expects him to assassinate Nero); and Vicki (who wants to explore more).
Barbara and the Doctor keep missing each other by seconds, French farce style, and in fact, the entire plot resolves without them meeting each other--the Doctor and Vicki think on their return that Barbara and Ian haven't budged since they left (they reprise their fridge schtick, playfight, and, er, make up...).
It's all a romp; the Doctor even violates his "Not one line!" rule against changing history--only for laughs:
Carry on, Doctor!