With Clarke trying to get into the Bunker, everyone figures out pretty quickly that they are stuck in there. Jaha confirms that there isn't another way out so to avoid things like cannibalism or killing their own people, the resources start to be saved. Food is given out in even smaller portions and that doesn't exactly help people.
Meanwhile, there are clans on different levels that are far from peaceful, with one of them attacking Jaha, Indra explains that they need a leader because for now they are doing whatever they want.
Kara, a new character on the show, ends up looking the entry way so her people and Kane and Abby and Jackson get to stay on the side with the food and the resources. She is looking out for her own people and wants to make sure Farm Station survives.
Octavia sees that Jaha was actually injured but he talks her through taking over the position of Commander, really taking it. He dies from his injuries. Octavia ends up threatening the people that are opposed to joining all the clans together. She goes on a public killing spree to make it clear that everyone is either going to be one group or they are the enemy and Octavia will kill them.
This leads up to her decision to make the fighting pits and they will serve as a way to bring about justice and also not worry about reducing the population, serving as the new version of getting floated.
Kane ends up in the fighting pits at the end, with it being alluded to the fact that he did it for Abby who has an addiction to pills now. He must fight to the death and if he is the last one standing then Octavia has to pardon him and announce him the winner. During that scene we see Kara must have won her own fighting pit and is now near Octavia, almost like her right hand woman.