Last night's episode of The 100 made some revelations and moved some plotlines forward, and the most interesting ones involved performing science experiments on human beings. But one topside plot and one underground plot involved the same idea: How do you destroy someone's sanity?
In fact, The 100 has been quietly boiling to this idea for a while. Lincoln is stuck in the Undergrounders' dungeon while a nicely dressed Dr. Frankenstein gets him addicted to some horrible substance (that in my head I am calling Ketracel-white). Frankenstein also gives him shock treatments timed with the sound of a tone...the same tone that chased off the Reapers who attacked Clarke and Anya. Well, that explains why the Undergrounders were able to control the Reapers—they made the Reapers. And we see how quickly the transformation happens when Lincoln is willing to go all killer gladiator on another test subject to get his next fix.
Lincoln's story runs in parallel to Finn's, who has been undergoing a transformation of his own. Finn isn't being conditioned by some mad scientist, though; he's being conditioned by his own response to the circumstances around him. And it becomes clear just how far gone he is when he and Murphy come upon a Grounder village (one with the healer that Octavia helped to free), and Finn undoes all of the goodwill Octavia earned by shooting up the villagers. When Clarke appears, having pursued him from Camp Jaha, he's deluded enough to think that he found her rather than the other way around.
Meanwhile, things in Camp Jaha remain tense. Clarke reunites with her mother, Bellamy, and Raven, but quickly defies her mother by sneaking away to find Finn. And when Abby confronts Raven about her role in helping Clarke and Bellamy's unauthorized mission, we get a great, "Do as I say, not as I do" moment. That is to say, Abby slaps Raven. Raven handles the outburst like a champ, though, reminding Abby that she already put Clarke in the gravest danger there was when she sent Clarke and the rest of them down to Earth to die.
And the situation under Mount Weather are no happier. Jasper learns that Clarke ran away, and he's debating whether he should go after her. But before he can make his decision, there is a containment breach in the dorm (which, weirdly, seems to be a genuine accident) and Maya is exposed to a lethal dose of radiation. Dr. Tsing, trying to sound very innocent, proposes that Jasper act as a human dialysis machine for Maya. Jasper quickly volunteers, but in the process, Monty starts to suspect that this isn't the first time Dr. Tsing has done something like this.
When the treatment proves a success, Tsing, our Frankenstein, and President Wallace meet to debrief. So it seems that the remaining 47 will find themselves as guinea pigs—or plain old medical equipment—sooner rather than later.