Octavia climbs down from the tower after killing Pike and finds Indra, still alive, being cut down from the cross she was put on. She tells Indra that ALIE is defeated and she killed Pike, but only after ALIE was defeated.
Bellamy and Clarke go outside and Clarke assures Bellamy that Octavia won't be charged with a crime for killing Pike. They survey the injured and dying people and wonder how to tell them about what ALIE told Clarke. Bellamy suggests keeping it secret until they figure out how to stop it. Clarke reluctantly agrees.
Clarke and Bellamy find a dead man being cried over in the street. Clarke realizes it's one of the men that Lexa killed to protect her in the City of Light. Outraged Grounders surround them, blaming "Wanheda" for what happened.
Back at Arkadia, Monty, Jasper, Harper, and Raven celebrate after ALIE's defeat and drink to it. Jasper apologizes to Harper for his actions while chipped. Raven is hesitant to celebrate until they know that everyone else is okay. Jasper still feels like he want to go back into the City of Light. He points out that, after being in the City of Light, Raven can now code -- ALIE "upgraded" her. Jasper grabs a gun, intending to step away privately and kill himself. Monty and Harper go off on their own. Raven attempts to contact Polis by radio.
Jaha and Kane leave the tower in Polis and see the enormous death toll. Abby helps the wounded. In penance, Jaha decides to help move dead bodies. Abby and Kane realize that the Grounders are looking menacing and blame them for the chip. Clarke tells her mother and Kane that they need to go back to Arkadia. Raven makes contact with them and they tell her what's going on and ask her to look into the radiation issue.
Roan is found, badly wounded from a gunshot but alive (barely). Clarke and Abby move to help him, but Echo holds a knife to Clarke's throat, refusing to let them treat Roan. Echo goads on the Grounders, telling them that this carnage is all Skaikru's fault. Echo declares Polis under Azgeda role. When another clan's ambassador challenges her, Echo suddenly beheads her to assert Azgeda's authority and instructs the Grounders to keep Skaikru in Polis.
Jaha attempts to help a grieving Grounder, but she rejects him. Murphy sees him and makes sure Jaha knows he believes that these dead are on Jaha's hands. Emori scavenges the dead for supplies, telling Murphy that it's not safe for her there. Murphy suggests going to Arkadia instead. Emori agrees.
The majority of Sky People in Polis are snuck out of Polis by some of the guards. Octavia, Bellamy, Clarke, Kane, and Abby remain behind. Clarke notices that her mother and Kane are clearly a couple. Indra and Kane reunite. Indra hugs him. Indra suggests going to war against Azgeda. Clarke tells the group that there isn't time for a war and Roan needs to be saved -- she confesses about the radiation levels rising and the clock running out for humanity. They formulate a plan for Bellamy to fake a surrender to Azgeda, as a distraction while Abby and Clarke sneak in to save Roan.
Jaha brings in the body of "Ontari" (wrapped) and is badly beaten by the Ice Nation warriors. Echo leaves to hear Bellamy's surrender, bringing Jaha with her.
While Bellamy is talking to Echo, Octavia (who was reallly in the body bag), busts out and slaughters the warriors guarding Roan as well as the healer who was working on him. Abby is disturbed by Octavia's violence, but she and Clarke quickly get to work on Roan.
Bellamy gives Murphy his gun, to hold a post while Bellamy is negotiating with Echo. Murphy quickly realizes that the situation is deteriorating and takes the gun, deciding that Emori was right and that they're better off on their own. Murphy and Emori flee Polis on their own.
While Bellamy is distracting Echo will false terms of surrender, Abby removes the bullet from Roan. Echo makes a crack about the murder of Trikru's army. When Bellamy attempts to keep Echo from leaving, Echo holds a knife to his throat, forcing the Sky People to disarm.
The Azgeda warriors find Abby, Clarke, and Octavia in the room with Roan. Echo is about to execute Clarke when Roan suddenly awakens and tells her to stop. Echo tells him that the Sky People killed Ontari and tries to convince Roan to kill Clarke and rule as King.
Meanwhile, back in Arkadia, Monty and Harper have sex and confirm their relationship. Raven bursts in, interrupting them, and informs them to get dressed because they're all going to die. In a separate room, Jasper listens to music and leaves a note for Monty, preparing to shoot himself. Before he can, Monty interrupts, bringing him to hear Raven's news. Raven informs them all that the nuclear plants are melting down and the world will end in six months, with it worsening before then, and they can't stop it.
Jasper laughs at the news, revealing his gun and putting it down, no longer wanting to kill himself since he'll die in six months anyway.
In Polis, Echo informs Roan that Clarke and her group are locked up while the rest of Skaikru has fled back to Arkadia. She continues to try to convince him that he needs to kill Clarke in order to regain the trust of the Ice Nation. Roan questions Echo's loyalty. She presents him with the Ice Nation crown, his grandfather's crown, insisting that he must give the order to exterminate both Trikru and the Sky People in order to establish his authority.
In lock-up, Abby comforts Clarke and acknowledges that she knows Clarke loved Lexa. Suddenly, Echo interrupts and has the guards take Clarke to Roan. He demands that everyone leave the room except for Clarke. Clarke tells Roan that the wave of radiation is coming that will kill off everything and insists that he needs the Sky People and their science to try to figure out a way to stop it. She begs him to recognize Skaikru as the thirteenth clan, so they can go back to Arkadia in an attempt to stop the end of the world. Roan points out that his people will kill him far sooner than six months if he doesn't kill her. She offers him the flame of the Commander in order to keep the clans in line behind him.
Roan accepts her deal and gives a speech to the assembled people, telling them that he will rule until another Nightblood is chosen. One young woman shouts that it is blasphemy for a non-priest to hold the flame. Roan tells everyone that he is honoring Lexa's coalition.
Echo gives Bellamy an emblem from Roan that will allow Skaikru to be protected in any of their lands. Bellamy and Clarke head back to Arkadia to work on a way to save everyone. Kane, Abby, and Octavia remain behind in Polis to help keep Roan on the throne.
Far away among the pyramids, bodies litter the radiation soaked landscape, having succumbed to radiation poisoning. A gruesomely sick woman stands atop a sand dune and allows a wave of radiation to sweep over her, literally disintegrating her body instantly.