The world of The 100 has gotten a bit more complicated than Grounders vs. Ark survivors, and with those more complicated factions come more complicated questions. And chief among those questions is "Do you deserve to survive if you harm other people to do it?"
That's a question that the people of Mount Weather don't feel they can afford to ask. After all, they would die each time they were exposed to the radiation-filled air if it weren't for their periodic harvesting of the Grounders. When Dr. Tsing realizes that Maya's blood transfusion from Jasper may have give her the ability to survive on the surface, the 47 become a much more appealing medical resource.
We learn that President Wallace's intentions for the (formerly) 48 were a little more benign—yes, he'd say whatever he needed to to keep them underground, but his goal was to feed and breed them, hoping their radiation tolerance would be passed down to the next generation. (And I was wrong last time, it looks like either Cage or Tsing was responsible for the breach that nearly killed Maya.)
It's interesting to see Wallace get all high and mighty with Cage and Tsing, telling them he doesn't deserve to see the sun if he sees it because he harmed the 47, but I can see where he is making a distinction between what he does to the Grounders and what the mad scientists want to do with the kids. For one thing, harvesting the Grounders is an issue of survival. The Undergrounders are sort of vampires, occasionally requiring the blood and kidneys of other people to stay alive. Perhaps he can even justify the creation of the Grounders the same way—the monsters are a way to keep their operation hidden. But Wallace has also expressed a degree of classism when it comes to the Grounders. Grounders are "savages," after all, while the children of the Ark can appreciate science, art, and chocolate cake. In the end, though, Wallace decides it will be alright to use the 47 as a more permanent radiation treatment, provided the kids consent.
But it turns out that Jasper's donation (and the sickness that followed) has left the rest of the 47 a little squirrelly. I'm a bit surprised their refusal was so uniform (surely someone thought that shelter and safety was worth a little vomiting), but perhaps no one has grown as close to an Undergrounder as Jasper has. And it turns out that friendliness goes both ways. Once Maya gets wind of the plan to use the rest of the 47 as radiation treatment, she reveals the awful, vampiric truth to Jasper and Monty. When she tries to defend the practice of trapping and harvesting Grounders, saying they have to do it to survive, Monty suggests that maybe they should just let themselves die. In the meantime, though, the 47 will play nice and submit to the transfusions to buy themselves time.
Harvesting Grounders is hardly the only of Mount Weather's atrocities, however. After Raven realizes that Mount Weather is jamming the communications between the Ark camps, she discovers Mount Weather's own communication band, in which they talk about controlling the Veil—that terrible acid fog. Mount Weather takes the business of a strong offense being the best defense to a disgusting new level.
And Octavia gets her first hint at the truth behind that other Mount Weather horror, the Reapers, when she encounters a freshly feral Lincoln. The sight of her doesn't even begin to touch Mount Weather's conditioning.
Knowing (in part) what Mount Weather is up to has had a profound effect on Clarke, as well. Her reunion with Finn wouldn't have been a happy one even if she hadn't seen the harvest chamber, but her time under the mountain has left her thinking about what people do in order to survive. Do the Ark survivors, with their superior firepower, deserve the Earth if they gun down unarmed Grounders? Should the Ark survivors be thinking about merely surviving, or making sure they retain their humanity along the way?
Meanwhile, Jaha and Kane are dealing with a slightly different question: how do they prove themselves worthy of survival? I was hoping that Thelonious had ended up far from Camp Jaha, but he actually finds himself captured by the same Grounders who are holding Kane. The Grounders place the two men in a cell with a woman who appears to be a prisoner and a knife; they're told that one man must kill the other before they can negotiate piece with the Grounder commander. A tense debate between the two men ensues: can one of them really go forward killing the other? Jaha rejects the idea, but Kane suggests that what the Grounders want his a human sacrifice, a show of good faith. Kane's even willing to turn the knife on himself.
When Jaha refuses to let Kane kill himself in the name of peace, the prisoner girl reveals herself as the real Grounder commander. She feels that Jaha and Kane's desire for peace is genuine, but she also wants the Sky People out of her territory. And after everything that's happened, we can't really blame her. So Jaha returns with a message: that Camp Jaha must move on or prepare for war. Of course, that would leave the 47 underground and the Grounders to deal with Mount Weather's abuse. And do the Ark survivors really deserve to survive if they do either?