Adelaide screams at the sight of Palmerdale's dead body.
Leela slaps her across the face, silencing her.
This is horrible. It's one of the relatively few examples of serious, realistic, non-Fantastic, gendered violence in the show. Companions are captured by monsters, etc., but this kind of thing happens rarely. It is better in some places. Worse in others. In 'The Time Meddler', Edith's implied-rape is in there simply to tick a box of genre tropes. Yeurch. In 'Vengeance on Varos', Maldak slaps Peri across the face to assuage his bruised ego. It's utterly gratuitous and revolting.
But this is a woman slapping another woman. (That's not worse... except in the sense that the representation, authored by a man, alibis male involvement in violence against women by ostensibly disappearing its gendered dimension.)
More than that - it's Leela slapping another woman. Wonderful Leela, who has never done anything like this before. Okay, she's a ruthless killer in battle... but slapping a 'hysteric' like she's James Bond or something? Normally, though she dreads weakness in herself because of her self-identification as a warrior, she is gentle and kind to the weak, to the scared. This is part of her warriors' code. She will be back to her real self in later stories. She's even kind to Adelaide later in this story.
What has actually happened here?
Somewhere along the line, Leela - or perhaps I should say, the character of Leela - has internalized the male attitudes of the time in which she is a visitor: the Edwardian era.
None of the male characters from that period physically abuse Adelaide, but Adelaide is secondary to almost all of them. To Palmerdale, she is a secretary and, probably, a mistress. Harker has no doubt about that, dismissing her as "the owner's fancy woman". Skinsale evidently desires her sexually, and also desires her esteem, yet finds her frustrating because she resolutely refuses to like him more than her boss. His delight whenever she becomes dependant upon him is evident. Vince Hawkins is the only person to whom she can feel comfortably superior, treating his bashful attentions as the services of a instrumentum vocale.
This story is all about class in many ways... but it is also about gender. In many ways, it's quite good on the subject. It depicts male attitudes in a non-exculpatory fashion. Leela is a forceful presence, crossing gender boundaries by putting on "men's clothes... working clothes", etc. Leela's actions and personality imply that Adelaide isn't just a dishrag because she's a woman; she's like that because she has been trained in a particular kind of social role owing to her gender and class... a role that involves men looking upon her with varying degrees of objectification and contempt, looks which they train at Leela but which bounce off her. There are other hints at these themes. Women as property. Reuben keeps pornographic pictures under his bed, for example.
But there is still a problem with that slap... which is that it comes from someone outside the Edwardian class system (this is, by the way, a depiction of the dynamics of that system that easily outclasses Downton Abbey or 'Human Nature'). The slap comes from Leela, who transgresses Edwardian sensibilities in so many ways.
Using what is sometimes charmingly called a 'real world point of view', this is probably to do with the fact that some 'Edwardian attitudes' had been internalised by the author of the story. (That this is going on in 1977 tells us a lot.) Employing a strategy I'm usually wary of - the redemptive reading - Leela's slap can be seen as evidence that even she starts to absorb psychological/ideological aspects of a heavily gendered oppressive system simply by being surrounded by it, by being locked in with it in a cramped space.
That's hegemony for you: you don't have to agree with the ideology in order for it to work on you.