Her ageing father informs her that due to his imminent dotage he must look to his daughter to sustain him, and suggests that the best way is for her to become a prostitute.
Oh, please go on the game; it's a steady job, and you'd be working from home!
Unconvinced, she decides to disguise herself as a boy, and seek her fortune in London, which her father attempts to point out the futility of.
Why walk all the way to London when you can make a fortune lying on your bed!?
Upon arrival in London, she is hired by Lord Blackadder while his manservant, Baldrick, is casually kicked out onto the streets. However, when Blackadder points out that "Kate" is a girl's name, she quickly claims it is short for "Bob". Blackadder becomes increasingly concerned about the attraction he feels for the boy. Eventually, after being prescribed a course of leeches by a doctor and an attempt to throw Bob out, he learns the truth, and several minutes later they become engaged. This is reminiscent of Shakespeare's Twelfth Night, in which the lead character, Viola, is forced to disguise herself as a man after a shipwreck. She, however, is hired by a Duke with whom she falls in love.
The wedding is due to be officiated by Lord Melchett, with Baldrick acting as bridesmaid (Kate didn't have any girl-chums, as her family was too poor to afford friends). Blackadder, mistaking him for a beggar, pays Kate's father £10 to go away, much to her dismay. Blackadder's promise to have Baldrick beat him up and retrieve the money does little to comfort her. Unfortunately Blackadder asks Lord Flashheart to be the best man. Shortly afterwards, Flash and Kate decide to run off together (although, as Kate has discovered she prefers wearing boys' clothes, and Flash feels more comfy in a dress, they swap outfits first), leaving Blackadder jilted at the altar.
In fact you're a girl with as much talent for disguise as a giraffe in dark glasses trying to get into a polar bears-only golf club
She begs Blackadder not to give her away, explaining that all her brothers have signed up, and she wants to see how a war is fought "so badly".
Well you've come to the right place, Bob. A war's not been fought this badly since Olaf the Hairy, High Chief of all the Vikings, accidentally ordered 80,000 battle helmets with the horns on the inside
While Blackadder isn't fooled, Lieutenant George is, failing to spot the truth even when she emerges from the shower wearing only a towel. So is Melchett, who, while attracted to the singer Gorgeous Georgina (utterly failing to recognise his family friend, the 6'3"-tall Lieutenant George), is outraged when she is replaced by what he perceives as a drag act involving Bob.
Driver Parkhurst also appears in the following episode, "Private Plane", once more involved with Lord Flashheart. Apparently she has become more open about her gender, and is now calling herself by the unisex "Bobbie" as well as wearing a woman's uniform. We are never told her real first name, though Bobbie was an acceptable shortened form of 'Roberta' for women in this period. 