Mark it here: The first real creative misstep of Doctor Who happens seven episodes in, and it's a doozy. It happens as soon as Susan sees Alydon for the first time, and responds to his appearance with the words, "...you're perfect."
There are really only two ways to read this scene. The first is that Terry Nation didn't think about the implications of having one of the four main characters respond to the appearance of a traditionally Aryan blond-haired, (metaphorically) blue-eyed white man by coding them as "perfect". That to him, that was completely obvious and the only reason Susan needed to comment on it was that it was unusual given what she'd been told about the Thals by the Daleks. I'm going to be immensely charitable here and not read it that way, because that's pretty much racism at its most overt and I don't think ill enough of Terry Nation to believe that he just assumed that white people were better than everybody else. Not less than twenty years after World War II, and not given that he makes the Daleks into Nazi analogues in every subsequent appearance.
The second, then, is that it's intended as deliberate irony that the pacifist Thals were once the aggressors, and their racial coding along with the suggestion that they were the ones who started the war is supposed to suggest that they're like post-war Germany. They're so traumatized by their own propensity for violence that they have rejected it utterly, and this is being exploited by monsters who have no scruples or principles. Which would code the Daleks as the Soviet Union, still paranoid after the last war and unwilling to see any kind of common ground with an enemy that nearly wiped them out. (Or as Israel, but again, choosing to not assume Nation is a horribly horribly racist person unless it's explictly coded as such.)
Which, okay, that's a fair enough reading, given that the Dalek plan to wipe them out seems to be portrayed in the story as a "preemptive retaliatory strike"; the Daleks can't even conceive of helping the Thals after all they've done to them, and they assume that the Thals will respond to a refusal of aid with violence, so the only option is to get their licks in first. But if that's the case--if that's the reading Nation is going with--then suggesting that the Thals need to renounce their pacifism and take up arms again, as he inevitably does in a couple of episodes, is pretty awful. In keeping with the character of the times, when the same people who completely and totally disarmed Germany and Japan then started to wonder why they weren't doing more to help us in the Cold War, but awful nonetheless.
But in some ways worse than all that...they're just so bloody twee! Every scene they're in, they undercut not just the drama of the story but the logic of the plot and the mood of the scene and basic common sense, to be perfectly blunt. We're told that their crops all failed, that they're a people on the edge of starvation and extinction who are reduced to begging their once-mortal enemies for mercy. But on-screen, they engage in middle-school banter about how "Alydon's got a girlfriend", lounge around in ridiculous outfits, and seem unconcerned with their situation except as a point of philosophy. They're polite and mannered to the point of absurdity--it's like watching Tolkien's elves stuck in the plot of Cormac McCarthy's 'The Road'.
Frankly, every time the story cuts back to them, it's like a splash of cold water in the face reminding you that you're really just watching a bunch of actors larking about on a cheap jungle set. Thank goodness the episode also contains the wonderfully tense jailbreak sequence that gives it its title, which is staged, shot and acted brilliantly, or this episode would be a disaster.