In Arkadia, tensions rise when Jasper uncovers the list of the 100 Sky People that Clarke decided should be allowed to live in Alpha Station if they're not able to find a way to save everyone. He accuses Clarke of playing god and Clarke retaliates by shocking him and locking him up to prevent him from revealing the list to their people.
Eventually, Monty (who is angry at Clarke for not putting Harper on the list) reveals the truth to everyone. The Sky People start to riot as Clarke explains that she had to choose strategically and that the list was skewed to young, strong women who could bare children to keep humanity going.
Jaha diffuses the situation by saying that they will abandon the list and hold a lottery to determine who will make the cut, with all those who work towards fixing the ship being allowed to enter it.
Meanwhile, tensions are also rising in Polis. Bellamy and Stevens, out on a hunt, are captured by Ice Nation and taken to Roan. Stevens reveals that the ship is being rebuilt and won't fit everyone. Roan is furious and easily convinced by Echo that they've been lied to.
Kane tries to explain that they are looking into manufacturing a serum to give everyone nightblood in order to survive, but Roan doesn't care. He has Stevens executed and locks Bellamy and Kane up. Octavia escapes after finding members of Trikru slaughtered by Ice Nation and informed that Azgeda has declared war on Trikru and Skaikru. She rides towards Arkadia to tell the others, but on the way, she's confronted by Echo.
Octavia and Echo fight and Octavia is stabbed and presumed dead. Back in Polis, Bellamy breaks down completely when Echo informs him of Octavia's death. In reality, Octavia survived her fall and rides her horse back to Arkadia.
Roan also informs Kane and Bellamy that they will all be riding back to Arkadia, which he intends to take, now knowing it's the only known secure facility.
Elsewhere, Abby, Jackson, Raven, Luna, Nyko, Emori, Murphy, and Miller are on a mission to Alie's island, where Jaha told them there is a lab where they can hopefully learn more about the nightblood that Becca created many years ago. Things are tense between Raven and Murphy (she still hates him), and between Luna and everyone (she is distrustful of their motives and feels forced into giving up her blood to save them all).
Suddenly, Alie's remaining drones (who are still guarding the island) attack. Nyko is killed and Luna makes a run for it. Raven eventually convinces Luna to remain with them and to help her get one of the downed drones, so that Raven can disable the others. Raven does this successfully, and everyone else survives.
The group enters the lab, where Raven and Abby seem hopeful about their prospects.