Yeah, so the adults on The 100 are no better at that "establishing a stable society on Earth" business than their kids are. But while they're trying to figure out the basics of crime and punishment, the kids are starting to piece together the details of a threat much larger than the Grounders.
Crime and Punishment
It was only a matter of time before Kane learned that Abby was responsible for arming the boys (and girl) and sending them off on a rescue mission to find Clarke and the others. Kane's first instinct is to imprison Abby, but he's kind of stuck. After all, it was just last episode that he announced that illicit firearms possession was a felony.
Major Byrne is the one who steps in and tells Kane that he has to carry out Abby's prescribed punishment, which involves a lashing with some sort of futuristic cattle prod. But we're left with an interesting contrast between the two women when a Grounder is captured with his injured child. Abby, before submitting to her electrical licks, immediately orders the Grounder child be taken to the medical camp for treatment. Byrne, on the other hand, who argued that punishment was a vital way to reestablish a sense of civilization, can barely keep her finger off the trigger while interrogating the Grounder.
We know which person Kane is more impressed by when he goes to Abby and has a conversation that goes roughly like this:
Abby: I'm not going to follow your rules unless I get what I want.
Kane: I'm going to give you what you want AND make you temporary chancellor of the camp.
Well okay, then. Yay, civilization?
The Case of the Missing Watch
Well, now we know what happened to Clarke's watch. When the boys (and girl) find the Grounder camp, they spot Clarke's watch hanging from one Grounder's neck. Looks like someone has been paid by the Undergrounders in shiny trinkets. After a good amount of beating and waving guns around, the boys learn that the Grounders from this particular village take their prisoners of war to a specific spot, where they're likely picked up by the Undergrounders.
A debate then starts among the group. Murphy wants to kill the Grounder since he knows where they're headed, but the others aren't on board with the idea. Well, it seems that way until Finn ends the discussion by coldly executing the fellow.
I repeat: Yay, civilization?
The Enemy of My Enemy is Not My Friend
Clarke frees Anya from her cage and the two of try to escape from Mount Weather and its vaguely vampiric denizens, which puts them right in Reaper territory. Clarke thinks they're going to work together, but Anya has other ideas, and ditches Clarke pretty quickly. But just as it looks like Clarke is about to get eaten, the Undergrounder scout team steps in with a sonic weapon that leaves the Reapers helpless. But they're not going to bring her back to the clean dorms and good food of Mount Weather's guest quarters; they're bringing her to "harvesting." We know what that means.
Just when things look darkest, Anya decides to rescue Clarke, and together they head for the exit, which is on the waterfall side of a dam. Clarke has her The Fugitive moment, and after appearing to consider surrender, she instead follows Anya down the waterfall.
But hey, Clarke? Anya is not your friend. Remember how you and yours blew up her soldiers? It turns out that the only reason that Anya saved Clarke from the Undergrounders is so that she could bring Clarke back to her people as a trophy. Nice.
The Cerberus Program
Octavia's storyline hasn't been particularly interesting in the season so far, but I get the impression that it will prove vital to peace with the Grounders down the line. She joins up with the Grounders from Lincoln's village and proves herself in battle, helping to rescue a group of the Grounder villagers. Lincoln isn't among them, but after releasing a primal howl of dismay, Octavia does get one thing from the Grounder leader: a respectful nod.
The villagers think Lincoln is dead, but actually, he's been taken to the Undergrounders, who, it turns out, are doing more than just harvesting the Grounders. Lincoln is tapped for something called the "Cerberus" program. And we know that only good things are named after hellhounds.