The ambassadors of the coalition (including Lexa and Clarke) bring Nia before them to stand accused of the attack at Mount Weather. When asked, Clarke demands justice for Skaikru. Titus proclaims death as the punishment for Nia's crime. Nia calls for a vote of no confidence, and many other ambassadors speak up, disavowing Lexa as Commander. Rather than execute all the traitors as Titus suggests, Lexa agrees to Nia's demand for single combat, to Clarke's and Titus' dismay. Lexa is to fight on her own behalf, while Roan is to be Queen Nia's fighter.
Back at Arkadia, Pike meets with Abby and Kane and attempts to convince them to retaliate for the attack. They refuse, citing that the war is against Lexa, not the Sky People. They were collateral damage. Abby adjourns the meeting and Pike leaves, upset.
Bellamy turns in his gear to Kane, resigning, believing that the deaths were his fault because he listened to Echo and left Mount Weather unprotected. Kane tries to convince him against it, and that he did the right thing. Bellamy refuses to accept that and leaves.
Nyko returns to Arkadia as everyone is preparing to go to the memorial at Mount Weather (except for Jasper, who refuses). Nyko brings with him sick Grounders. One of Pike's guards refuses to let them enter, but Octavia brushes him aside and brings the Grounders in.
Jasper sneaks out of the camp by making an opening in the fence. Monty reluctantly follows him.
Lexa gives a pep talk to the gathered Nightbloods before their training. Clarke arrives to talk Lexa out of fighting. Lexa dismisses the Nightblood children, except for Aden, who she introduces as the most promising Nightblood initiate. Aden will likely take Lexa's place as Heda if Lexa dies in the fight with Roan. At Lexa's prompting, Aden swears loyalty and protection to Skaikru, the 13th clan, should he succeed Lexa. Lexa also informs Clarke that Indra has been sent to gather a Grounder army to keep Arkadia safe.
Aden is dismissed and Clarke tries to convince Lexa not to go forward with it because she stands no chance against Roan. Lexa explains that if Clarke is right, Lexa's spirit will choose another commander and Clarke must accept that. Clarke refuses and leaves.
Queen Nia gives Roan a pep talk before the fight. She tells him that their people will be stronger than ever when he kills Lexa, and that his banishment will be over. She admits that everything she does is for Azgeda. She gives him a sword and asks Roan to at least fight for his clan and bring her Lexa's head.
Clarke visits Roan and attempts to convince Roan to betray his mother and become the king instead of killing Lexa. She points out to him that his mother was willing to let him die, and that there is nothing to stop her from banishing him again. He refuses, saying that his people wouldn't take him back if he betrayed her -- but he is willing to help Clarke kill Queen Nia.
Pike gives a rousing speech at the Mount Weather memorial. Bellamy gives a brief eulogy for Gina before Pike's men interrupt the memorial to tell Pike about Indra's Grounder army near the camp. Pike confronts Kane and Abby, not believing their assurances that it is a peace-keeping force sent by Lexa for the Sky People's protection. Pike riles up the crowd, demanding that they tell Indra's army to go home. A few Sky People move to attack Lincoln for being an outsider and a fight breaks out, with one of them injuring Lincoln's head. The fight disbands at Pike's command and Lincoln staggers off, hurt, before picking himself back up again.
Jasper and Monty arrive at Mount Weather. Jasper is drunk and continues to drink to the memory of the deceased at Mount Weather. Monty looks through Jasper's backpack when Jasper goes off to urinate. He finds what appears to be a jar of ashes with a whole tooth in it -- Finn's ashes. When he goes to confront Jasper, he finds Jasper laid out unconscious near the entrance of Mount Weather and sits next to him.
Abby patches Lincoln up. Lincoln refuses to press charges against the man who attacked him. Pike thanks him. Octavia goes to see Lincoln. She tries to convince him that since Lexa lifted the kill order on him, she might take them back and they can get away. Lincoln refuses, wanting to stay and show the Sky People that all Grounders are not Azgeda.
Clarke visits Queen Nia, offering to change her vote to be against Lexa in exchange for her own protection and protection for Skaikru. Clarke offers a blood oath to seal the deal. Ontari stops Nia right before Nia cuts her own hand -- she realized that Clarke surreptitiously poisoned the blade, intending to assassinate Nia. Nia denounces Clarke and declares that she and her people are enemies of Azgeda. She cuts Ontari's hand and drips Ontari's black blood onto Clarke's face, to send a message to Lexa: Ontari has night's blood as well, and she will be the next Commander.
Clarke reports back to Titus and Lexa, who are alarmed that Ontari has night's blood. All children with night's blood are supposed to be brought to Polis and trained to be potential commanders. Clarke and Titus try to convince Lexa that she is playing into Nia's hand. Clarke insists that she will not just sit there and let Lexa die. Lexa bids farewell to Clarke and heads off to the fight.
Pike talks to Bellamy in the cafeteria about Bellamy resigning. They drink together. He tells Bellamy that the massacre was Bellamy's fault -- as well as Pike's, because they both trusted a Grounder. They drink to never making the mistake of trusting a Grounder again. Pike convinces Bellamy to help him steal ten automatic guns for Pike's men, to take out the Grounders surrounding them and protect their people. Pike tells Bellamy that regardless of it being treason, he is willing to pay that price to save their people. Bellamy concurs.
Clarke arrives to watch the fight and Lexa tells her she's glad Clarke came. The single combat between Lexa and Roan begins. At first, Roan has the upper hand, but Lexa suddenly overpowers him. Nia shouts that if Roan dies, he shall not die a a prince but as a coward. Lexa suddenly turns and throws her weapon at Nia, impaling and killing her. She declares the queen dead and long life to the new king (Roan). The crowd cheers for Heda.
Bellamy, Pike, and Pike's men attempt to leave the camp with the stolen weapons to take out the Grounders. They run into Harper, Monroe and Lincoln who attempt to stop them. Bellamy gets Monroe and Harper to step aside but Lincoln refuses, taking hostage one of the gunmen in order to get them to stop. Abby, Kane and the rest of the camp come out at the sound of the alarm. Pike again emphasizes the need for preemptive attack, while Abby and Kane refuse and order Pike to be locked up along with the other gun-toting men. One of Pike's men suggests that Pike's name be added to the ballot for chancellor the next day. As they're led away, Bellamy leads a chant of Pike's name, to Abby, Kane, Octavia, and Lincoln's horror.
Jasper wakes up and Monty confronts him for having stolen Finn's ashes from Abby. Jasper threatens to scatter the ashes, though Monty tries to convince him not to do it for Raven's and Clarke's sakes. Jasper wonders how Monty could have killed all of those Mountain Men and been fine with it, while Jasper is so destroyed. Monty tells Jasper that he is not fine with it and that he is tired of watching Jasper's self-destruction. Monty leaves and Jasper accidentally stumbles and spills out Finn's ashes, to his horror and distress.
Back at Polis, Clarke prepares for bed and is visited by Lexa. Clarke offers to change her hand bandage, and they sit on Clarke's bed while she does so. They discuss Ontari. Lexa says that Ontari won't be back until the conclave after Lexa's death, when the next commander is chosen. Lexa thanks Clarke for backing her. Clarke says she was only doing what was right for her people. Clarke notes that Lexa's ambassadors betrayed her and wonders how Lexa can forgive them and move forward. Lexa believes they were only doing what was right for their people. They part for bed.
Kane visits Pike in lock-up and reports to him that Pike won the election. He hands over the pin. Pike performs three acts as Chancellor: he pardons himself and the others, rejects the brand that made the Sky People the thirteenth clan, and brings his people to finish what they started in taking out the Grounders. Kane tries to stop Bellamy, but Bellamy goes along anyway.