Clarke overlooks Polis from her prison cell in the tower. Lexa enters and tells her she has allowed Clarke to refuse to see her for a week but she is holding a summit at sundown with the Skaikru and will be returning Clarke to her people. She tells Clarke she saved her and Clarke gets angry about Lexa leaving her at Mount Weather, saying the difference between them is that Lexa had no honor and Clarke had no choice. Lexa tells her she wants the Skaikru to become her people and join the Coalition as the thirteenth clan. If Clarke bows before Lexa, the Skaikru will be safe. Clarke tells her to kill her for the power of Wanheda and refuses to ever bow before Lexa.
Lexa enters the throne room where the representatives from the rest of the clans have gathered. All bow before her except for the Ice Nation representative. Titus confronts him and the Ice Nation representative tells him the Commander should bow before him because they don't make treaties with enemies. Titus tells him that the Commander bows before no one. Lexa switches to English in honor of the Skaikru who have yet to arrive and tells Titus to stand down. The Ice Nation rep asks why Wanheda is still alive and calls Clarke Lexa's "weakness." Titus asks about the Ice Nation army that moved in close to Polis and he excuses it as "military exercises." Indra calls him out on crossing the border of Trikru lands. Lexa calls a halt to the argument and invites the Ice Nation representative to join her to speak in private on the balcony where she has a message to deliver to Queen Nia. She kicks him off the balcony, killing him, and turns around to ask if anyone else wants to question her.
Outside Polis, a truck arrives carrying the Sky People. Kane exits and tells everyone to leave their guns and radios in the truck and Lexa's guards will escort them to the summit. He tells Nelson and Hill to remain behind in the truck and man the radio. He notices one of the Arkadia Guards has a med kit from Mount Weather and orders him to leave it behind. Abby tells him to not take out his anger on the guard and Kane responds that she put their entire summit agenda at risk by moving people into Mount Weather. Abby tries to excuse herself by saying she did it to save Nyko but Kane tells her opening a hospital is different than moving into the Mountain and now they will have to add that to the list of objectives for the summit meeting: lifting Lincoln's kill order, opening trade, and getting Clarke back. He quickly apologizes for using Clarke as a bargaining chip but Abby worries they will not get Clarke back.
A rover pulls up to Mount Weather and Bellamy, Raven, Gina, and Octavia exit. Bellamy complains to Gina about not being at the summit because Kane is trying to teach Bellamy a lesson. They bring supplies into Mount Weather and enter the dining room on Level 5, finding it filled with Farm Station survivors, eating and having fun. Pike welcomes them and both Raven and Octavia are uncomfortable with how they made themselves at home. Pike tells them there are thirty-six people there. Octavia warns the Grounders are going to think the Sky People have moved into Mount Weather before leaving in disgust. Sinclair arrives and tells Raven to get working on the electrical problems.
In Polis, Clarke is approached by Roan, who is also being kept prisoner by the Commander. Roan tells Clarke that Lexa broke the deal with him by not lifting his banishment when he delivered Clarke to her and now he wants to strike a deal with Clarke. He bought off some of the guards and has left a knife under Clarke's bed to kill Lexa and with Lexa dead, the Ice Queen will become ruler of the Coalition. Clarke says she sounds worse than Lexa but Roan tells her it is because she only has heard Lexa's side of it.
Bellamy finds Octavia sitting on top of the side-door to Mount Weather. He asks her if she's okay and then climbs up to join her. She tells him that inhabiting Mount Weather is a mistake. Octavia reveals to Bellamy that once the kill order is lifted off Lincoln, they will finally be able to leave. She apologizes for not fitting in with the Sky People. Bellamy is understanding and tells her that she will always fit in with him. Two Farm Station survivors enter the clearing escorting a prisoner with them. Bellamy recognizes Echo, who has been taken captive for "threatening the summit." Bellamy and Octavia free her to the protests of the Farm Station guards and Echo tells them the summit is a trap and all of the Sky People will die.
In an unknown location, the Ice Nation assassin lays out a set of knives before pulling back his hood to reveal bleeding cuts on his face.
In Mount Weather, the lights are flickering on and off as Raven and Gina make their way with Sinclair to the mess hall, having been called there in an emergency. In the mess hall, as Pike and Bellamy question Echo, other Farm Station members are grabbing weapons and arming themselves. Echo tells them the summit is a trap. Bellamy tells Pike they can trust Echo because she saved his life. Sinclair arrives and he and Pike get into an argument about using the missiles in Mount Weather. Raven says she might be able to help get the launch codes. Bellamy tells Gina to remain behind to help them find the launch codes while he leaves for Polis to warn the rest of the Sky People about the attack since they are not responding to the radio.
The Ice Nation assassin sets out a digital watch with a countdown on it. He slices the palm of his hand and drips blood into a receptacle.
Kane arrives in Polis, seeing it for the first time above-ground and is amazed at the sight. He wanders through a marketplace with Abby and their guards as they take in everything. A girl grabs Abby's hand and drags her to a kiosk where a woman is frying up some local food and offers a piece to Abby but Abby refuses. Kane happily accepts the food and offers the woman the patch off his jacket in exchange. Abby sees that Kane has a vision for their people and offers him the Chancellor's pin but he refuses, saying they should hold an election instead of passing the pin around. Indra arrives and welcomes them to the capitol.
Outside Polis in the woods, Lexa is training with Aden while the other "Nightbloods" watch. Aden gets a hit just as Titus announces the Sky People have arrived. He orders the Nightbloods to pair up and continue training. Lexa tells him that Aden is better than she was before her Conclave. They discuss the summit and Titus warns her about antagonizing the Ice Queen by offering the Sky People a seat at the summit. He asks why she is having the Sky People join the Coalition when they are there for a treaty and the rest of the clans will not agree to it. Lexa says everyone will agree when they see Wanheda bow before her. He tells her if she wants Wanheda's power, she needs to kill Clarke.
Sinclair, Raven, and Gina are digging through the computer files in the Mount Weather Command Center as they look for the codes to the missiles. Gina suggests that Dante might have written down the passcodes and leaves to check the President's office for the codes.
Bellamy, Octavia, Echo, and Pike arrive at the outskirts of Polis and park behind the truck Kane and Abby arrived in. Octavia discovers the two guards Kane left behind had their throats slit and that is why they did not respond when radioed about the threat. Pike starts to go after Echo but Octavia steps in and tells him that Echo warned them. Octavia tells Echo she is not leaving her blade behind before entering Polis and Echo says she will take them through the tunnels so they can keep their weapons.
Clarke sits in her room, contemplating the knife Roan left behind for her. Lexa enters and Clarke whirls around, pressing the knife to Lexa's throat. Neither move for a moment before Lexa apologizes. Clarke drops the knife in defeat. Lexa tells Clarke she is free to go and will be escorted to her mother. Clarke tells Lexa she has a better idea.
Abby and Kane are in Lexa's bedroom, waiting for her to arrive. The door opens behind them and Clarke walks in. Abby is overjoyed to see her and hugs her. Clarke gets down to business and tells them the terms of the summit have changed because of the Ice Nation. They are no longer there for a treaty but to join the Coalition to avoid a war. Abby refuses and Clarke calls it their new Unity Day where the Sky People can either be the thirteenth station or the thirteenth clan. Abby asks for Kane's advice and he agrees with Clarke.
At sundown, the summit begins with the Grounder Anthem as Clarke strides into the throne room and takes a stand before Lexa.
Under Polis, Bellamy, Echo, Octavia, and Pike move through the tunnels toward the elevator shaft to the Polis tower. Two guards spinning the wheel that raises and lowers the elevator are in their way.
The Ice Nation assassin paints himself in the blood he spilled earlier as he says out loud he is doing it for his father, mother, brother, and kin.
Clarke pauses in front of Lexa before dropping down on one knee and bowing to her.
Pike and Bellamy attack and kill the two guards running the elevator.
Roan is the first to bow to Lexa after Clarke and the rest of the people follow suit with Kane, Abby, and the rest of the Skaikru as the last kneel.
Octavia is upset that they killed the guards when they did not have to. Bellamy insists they did. They proceed to climb the ladder up the elevator shaft to the top floor.
Lexa orders everyone to rise and welcomes the Skaikru and Clarke to the summit. She tells the rest of the clans she is initiating them into the Coalition and the leader of the Skaikru will bear the mark. Abby passes the leadership over to Kane and he offers his forearm to be branded with the mark of the Coalition. Octavia, Bellamy, and Pike barge in, holding a guard captive. Bellamy warns everyone the summit is a trap. Ivon, the Ice Nation representative, tells them it was the Skaikru who barged into the summit with guns. Pike says they are right because two Skaikru guards are already dead. Lexa asks how they came by the information and Octavia realizes Echo is no longer with them.
The timer on the digital watch goes off and the Ice Nation assassin completes his ritual and pulls his hood back up. He moves through the halls, revealing he is on Level 7 of Mount Weather.
In the Command Center of Mount Weather, both Raven and Sinclair still have not found the launch codes. Raven gets frustrated and gives up because it is already dark and they are too late. Sinclair tells her she is someone who does not give up. He says that if she knows of a way to fix something, she fixes it and the reason she won't fix herself is because she feels she deserves it. Raven asks if she is just broken. Sinclair reminds her that he took a chance on her even with her heart defect and she should take a chance on herself, too. Gina radios in that she has not found anything in the president's office as the Ice Nation assassin arrives behind her and stabs her, mortally wounding her. Raven keeps trying to reach Gina as the assassin clears off the president's desk and triggers a monitor to access the program for Mount Weather's self-destruct feature. He exposes a set of numbers written on his forearm and punches them in, setting it to go off in one minute and leaves. Gina reaches the radio and tells Raven about the self-destruct and the assassin. Raven and Sinclair chase after the assassin as he runs out the side-door of the Mountain. Sinclair gets tackled by the assassin and they fight, with the assassin getting the upper hand. Raven arrives in time and shoots the assassin dead. Sinclair gets the numbers as Raven tries to reach Gina but Gina is not responding. She starts to head back into the Mountain as Sinclair tries to stop her. Gina is dead, the countdown reaching zero reflects off Gina's eye and Mount Weather explodes, throwing Raven and Sinclair back and killing all of the Farm Station survivors who were inside.
At the summit, Bellamy realizes Echo betrayed them as Kane tells him to stand down. Raven comes across the radio and tells them that the Grounders attacked Mount Weather and it is completely gone with only her and Sinclair surviving. Ivon tells them that is what they get for moving their people back into Mount Weather and the Ice Nation did what Lexa was too weak to do. Lexa declares war and orders the Ice Nation delegation along with Prince Roan to be arrested. Abby worries that Arkadia might be under attack next and Lexa commands them to go. Indra offers to escort them and tells Octavia she hopes she kept up on her training because she will need it before giving her back her sword. Bellamy tells Clarke they need to leave while Lexa offers Clarke protection if she remains as Skaikru ambassador. Clarke tells them she is staying to make sure Lexa keeps her word. Bellamy warns Clarke that Lexa will always put her people first and tells her to come home but Clarke apologizes and stays.
Later, Titus leaves Lexa and Clarke alone in the summit room. Clarke questions how the Ice Nation got the launch codes. Lexa thanks her for staying. Clarke tells her she stayed for her people and Lexa had better not betray her again. Lexa tells her she won't and then kneels before Clarke, swearing fealty to Clarke. Clarke offers her hand and helps Lexa rise back to her feet.
In the woods outside Polis, Echo walks through a gathering of several ambassadors from the 12 Clans, saying she has a message for the Queen. Echo tells Nia that she got her war, thanks to the Last Mountain Man. Lieutenant Emerson steps forward, revealing he was the one who provided the assassin with the codes to destroy Mount Weather. Echo tells them Clarke is by Lexa's side, as predicted and her son is a prisoner. Nia promises Roan will soon be free and Lexa will be dead.