At the camp, the delinquents are listening in through remote broadcast as Chancellor Jaha gives a Unity Day Celebration speech on the Ark about how everyone will be on the ground next year. Clarke walks up to Finn and he tells her how Unity Day is a lie because the Ark only came together after the 13th station was blown up. Clarke tells him that peace came out of that violence but Finn questions whether there even needed to be violence. Jasper comes out with a batch of "Unity Juice" from Monty's still. As Jasper is serving up drinks, Finn watches Octavia sneak out of camp.
Jaha continues his speech up on the Ark, telling everyone gathered that the first Exodus ship will be coming down in 60 hours with reinforcements. Everyone claps and Diana Sydney approaches Abby to ask if there are any hard feelings about her taking Abby's Council seat. Jaha cuts his speech short to begin the Unity Day pageant and Diana remarks on it before leaving. Jaha then introduces the children who will be performing "The Story of Us." Vera Kane approaches her son, Marcus Kane, and asks him if he will take the "last tree" down with him but he brushes her off. She then asks if he'll at least recite the Traveler's Blessing as a goodbye gift for her. He tells her he doesn't remember it and steps away. A girl in the pageant begins reciting how long ago, 12 Stations were floating alone when they decided to join together. Suddenly, an explosion rockets through the room. Jaha's ears are ringing as he crouches next to the injured girl who was telling the story. Arkers are lying unconscious or dead and people are scrambling to help. Abby asks if Jaha is okay and Jaha tells Kane to find out who did this. Kane finds his mother dying, impaled with a shard of metal. Abby comes over to help, but there isn't anything she can do. Kane holds his mother and delivers to the travelers blessing, "in peace, may you leave the shore. In love, may you find the next. Safe passage on your travels until our final journey to the ground. May we meet again." Kane realizes that four members of the Council are dead and tells Jaha that it was a coup and they need to get him out of there. They realize that Diana is missing and Jaha orders a lock-down while Kane goes looking for her.
Lt. Graco goes searching for Diana and Cuyler Ridley and warns them that they suspect Diana was behind the bomb. Diana tells Ridley to get the Exodus ship ready so they can take it. Ridley warns them that speeding up the charging of the ship will cause disruptions on the Ark and people will die. Diana tells him to take the Exodus ship anyway.
Back at the camp, the delinquents are drinking and celebrating. Clarke approaches Bellamy and he tells her he has security covered in case Lincoln comes back with other Grounders. He tells her she could use a drink and reminds her that in two days, her mom is coming down and the party is over. Clarke agrees and tells him he also deserves some fun. Bellamy jokes that he'll have his fun when the Grounders fun. Meanwhile, Raven is busy taking apart bullets when Finn comes in and asks why she's helping Bellamy. She tells him she volunteered and Finn tells her they could try talking to the Grounders. Raven asks him why he is defending Lincoln but he leaves without answering her question.
Octavia is out in the woods on her way to Lincoln's cave. She finds he left her white flowers and she picks them up with a smile. She tries to sneak up on him in his cave, at first looking like she's going to kill him since he has been training her to be a warrior. He tells her she is getting better and it is then revealed that the two are now lovers. Afterward, as Lincoln helps Octavia back out of his cave, Finn suddenly appears, brandishing the blade that Lincoln had stabbed him with. Finn suggests forming a truce between the Grounders and the delinquents and Lincoln agrees. The three arrange a meeting between his leader (Anya) and Clarke.
Kane and Abby are at the Exodus ship as Abby packs medical supplies. Diana comes running up and tells them they need to delay the launch because a mechanic, Cuyler Ridley, is the terrorist who planted the bomb because his wife died in the Culling and he has turned himself in. Kane questions Diana on why she left the pageant early and she tells him she was lucky. Kane then leaves to question Ridley.
At the camp, Clarke is playing drinking games with Sterling, Fox, and Miller when Finn interrupts and pulls Clarke away. He tells her about the meeting he set up with the Grounders. He tells her he thinks they can do better this time around and Clarke says they need to bring backup. Finn says the agreed terms were no weapons. Clarke agrees and tells him she'll meet him at the gate. She then seeks out Bellamy and tells him about the meeting, asking him to come as her backup without telling Finn. Meanwhile, Jasper finds Raven working on the bullets and tries to recruit her for a drinking game against Monroe. He starts helping her with the bullets because he was "great in chemistry" and talks about his parents before asking Raven about her family. She tells him, "just Finn," and Jasper replies that they all have each other now. Bellamy enters and tells Jasper he's coming with him and he needs guns and ammo. Raven tells him she's coming with them. Jasper takes one last swig of alcohol before leaving.
Clarke and Finn are walking through the woods and Clarke stops to check his stab wound. She tells him she's just trying to keep them alive. As they continue on to the meeting place, Clarke leaves behind a trail that Bellamy, Raven, and Jasper are following.
On the Ark, Kane enters a prison cell with Lt. Graco and another Ark guard and starts interrogating Ridley about the bombing. Ridley tells Kane that workers all over the Ark are getting fed up since it was their kids who were sent to Earth, yet they don't get to be on the first drop ship. Lt. Graco pulls out his shock baton and shocks the other guard as Ridley kicks Kane over and breaks free. Lt. Graco and Ridley lock them in the prison cell, saying they're going to die in there anyway just as the power starts flickering. In the Command Center, Jaha asks Sinclair what is happening and Sinclair tells him that people are going to start freezing to death. Jaha lifts the lock-down to get people out of the danger zones and asks where Kane is. Sinclair tells him he's in the prison station, where the power is out. Jaha finds Kane and Kane tells him it's a mutiny. At the Exodus ship, Abby is preparing medical supplies while talking to Red, a mechanic, when Diana and her people take over the drop ship. Red makes a run for it back to the Ark and Diana tells them to let him go because she is going to lead everyone else home.
Clarke and Finn arrive at the meeting place on a bridge where Octavia is waiting. Clarke realizes it was Octavia who set it up and Octavia tells Clarke that she trusts Lincoln. Lincoln comes running up shortly thereafter and catches Octavia in a hug, which Bellamy, Raven, and Jasper witness from their hidden location under the bridge. Bellamy gets Lincoln in his sights just as the Grounders arrive on horses. Finn gets upset when he sees they are carrying weapons. Clarke crosses the bridge and meets Anya in the middle and offers her hand, which Anya doesn't shake. Anya tells Clarke that she started a war she doesn't know how to finish when she burned a village to the ground with the flares they set off trying to alert the Ark they were alive. The delinquents invaded their land and sent an armed raiding party to capture and torture one of their people. All those actions are acts of war.
On the Ark, Red, Jaha, and Sinclair are trying to get the door opened to the drop ship to prevent them from launching it. Ridley finds Abby hiding in the bay and brings her to Diana. Diana asks Abby to come with them because they would need a doctor and Abby owes no loyalty to Jaha, the man who floated her husband and she'd be able to see Clarke again. Instead, Abby runs and tries to open the door for Jaha and is baton-shocked by one of Diana's guards but the door opens enough for Red to get his pry-bar in.
Anya asks Clarke if it's true that more warriors are coming down and Clarke tells her that yes, there will be Ark Guards, but also farmers, doctors, and engineers. Anya asks if Clarke can promise that they'll agree to the terms she and Clarke agree on but Clarke can't promise that. Meanwhile, Jasper spots Grounders in the trees and shouts at everyone to run as he starts shooting at them. Anya's warriors shoot arrows back at the delinquents. Anya takes out her knife and is about to stab Clarke when Bellamy shoots her in her arm. Finn runs across the bridge to drag Clarke to safety. Jasper, Raven, and Bellamy take off running as an arrow flies toward Octavia. Lincoln shields her and is hit in the shoulder with it. He breaks it off, saying it's only a scratch. Lincoln tells them to keep running till they get back to their camp.
On the Ark, they are still trying to pry the door open when Sinclair realizes they haven't decoupled the dropship from the Ark, meaning that all of the systems on the Ark will be crippled and everyone will die if the dropship launches. Jaha begs Diana to not do this and Diana tells everyone the truth: there aren't enough drop ships to get everyone to the ground. Red tells Jaha he doesn't trust either of them but he's going to the ground. He climbs through the door to the dropship and knocks the jack loose, sealing to the door so the drop ship can launch. The drop ship yanks away from the Ark, causing the power to go out and catastrophic damage across the Ark.
After the failed meeting at the bridge, everyone returns to camp and start blaming each other for everything. Finn blames Clarke for bringing guns and for not trusting him, blames Raven for being too preoccupied making bullets, and blames Jasper for firing the first shot. Clarke blames Finn for trusting the Grounders. Raven blames Finn for not telling her about it. And Octavia blames Jasper for ruining everything before walking away. There is a sonic boom and Clarke and Bellamy look up to witness the Exodus ship coming down a day early, much too fast, and without a parachute. An explosion is seen in the distance and Clarke crumples in grief when she realizes her mom is dead.
Finn: "I could ask you the same thing. I could also ask like how long you've known he speaks English? But, I won't. (indicates blowhorn) You blew this when your people were hunting us - you saved our lives. I have to believe there’s more like you.”
Diana Sydney: "We could use a doctor on the ground. Come with us. You owe Jaha no loyalty. He's killed your husband and betrayed you. You're just like us. Think of your daughter, Abby. You can see Clarke again today."