Clarke and the others arrive in Sanctum. Cadogan takes control of Sanctum and has Sheidheda injured. Gabriel is meant to heal him but then he realizes that the red sun toxin is moving in. He decides not to take the antidote because he sees Josephine and wants her around. Josephine starts to convince Gabriel to use the machine from the mind drives to collect information from the flame. Then he could offer to take the final test since he has nightblood and he would see what the answers are.
Sheidheda and Indra are tied up prisoners together. They decide to work side by side to get out, but then Indra starts to see the memories of her mom kneeling to Sheidheda. She decides not to free Sheidheda, but she doesn't kill him either. She leaves him to bleed out.
Meanwhile Clarke goes off to get the flame and Cadogan and Bellamy stay behind. Bellamy and Cadogan talk about their beliefs. Bellamy can't seem to connect with his people. Raven is struggling with her past in the reactor. Nikki finds her but instead of killing her she decides to leave her to deal with the deaths she caused.
The red sun appears so everyone has to hide and Madi reveals to Clarke that Cadogan shouldn't use the flame because she has memories and it doesn't look good. When Gabriel arrives he proposes his plan with the flame but then he changes his mind and shoots it. Things escalate so Clarke demands that Cadogan takes them to their people on the offline planet that he sent them too.
The Conductor gets killed when he jumps in front of Cadogan to defend him from a stray bullet.
Sheidheda tells Bellamy about the sketchbook and he says Cadogan needs to see it. Clarke and him go back and forth. Clarke says she will shoot Bellamy if he passes the book to Cadogan through a disciple. Bellamy says Clarke won't shoot him. She does. She kills him and leaves into the Anomaly.