Clarke and Lexa
In Polis, Clarke and Lexa are lounging in her throne room. Clarke draws Lexa while she sleeps until Lexa is awakened from a nightmare of the deaths of the previous commanders. She fears it is a warning, and that she is betraying their legacy. But Clarke assures her that the ceasefire is leading to a legacy of peace. Titus enters the throne room with a "gift" from King Roan, as proof of loyalty to the Coalition. This gift is revealed to be Carl Emerson. Albeit being bound, he still attacks Clarke on sight before Lexa orders him to be locked away immediately. Later, Lexa, Clarke, and Titus discuss whether or not they will execute Emerson. Clarke, much to Lexa's reproach, says he deserves to die.
Somewhere in Trikru territories, Octavia spies on Hannah, Gilmer, and a few more of Pike's followers as they take soil and water samples. A Grounder kid appears, walking peacefully, and is attacked and hunted on the order of Hannah, as he has seen what the Sky People have been up to. Octavia saves him but is burned by poisonous tree sap to do so. The kid runs off and escapes back to his village. Octavia reports to Kane that they need to find out what they are doing, as they are willing to kill a child to keep it secret.
Back in Arkadia, Abby checks up on Raven, who is acting abnormally pleasant from taking the pill that Jaha gave her, calling it the "key to the City of Light." Later it is seen by Abby and Jasper that Jaha is still distributing the pills. Jaha and A.L.I.E. ask Raven if she can search for A.L.I.E.'s "Version 2." Raven asks if there is something wrong, which Jaha curtly denies.
Miller helps Kane put a bug in the Chancellor's office. Pike plans to grow crops in the fertile soil in the area. Monty Green points out that there is a farming village in that area, where Pike wants to go. He explains that with the loss of Mount Weather's resources, Arkadia will starve in less than a year, and that the village will not attack after they destroyed the army. Monty explains that the Grounders will retaliate no matter what. At the end of the meeting, Pike asks if they will fight for their home. Bellamy says he will fight for Arkadia, upsetting Octavia, who was also listening in on the meeting.
Octavia heads to the village, where she is attacked by their leader, Semet, until she is vouched for by the boy she saved, Gavriel. This only lasts for a little while until the Grounders start preparing for an ambush, making bonfires out of the same poisonous tree sap that burned Octavia's forehead, who is later knocked unconscious by a villager. In Arkadia, Kane speaks to Abby about his regret for demanding an election. She comforts Kane, telling him that the surviving members of the 100 are no longer just kids. Abby kisses him on the cheek and gives him "hope."
Raven patches A.L.I.E. into the grid. Jasper asks Raven what drug she is on and where he can get it. She directs him to Jaha. As Jaha and A.L.I.E. are about to let Jasper take the key, Abby intervenes. Jaha explains that the pill is a silicon-based device that interrupts pain receptors. She worries there may be side effects, and asks if he would have given it to Wells without testing it first. Jaha seems confused, saying, "Wells?" He does not remember who his own son is until A.L.I.E. has to remind him. Abby, realizing that the pills are eliminating more than just pain, but also painful memories, stops Jaha from distributing them anymore. He does not want them to stop giving people the keys, and it turns out that Jackson was given the key as well, saying he will keep an eye on her.
Meanwhile, Clarke confronts Emerson, who is chained up in front of Lexa's throne. He shows his resentment and hatred toward her for destroying the Mountain, and killing his two children along with it. As Clarke leaves, Emerson says his pain will end when he dies, but hers has just begun. Titus waits in her chamber, and they discuss Lexa's decision, which he fears will get her killed.
As Bellamy's group arrive, they find the village empty. The Grounders are revealed to have planned an attack from above, firing down flaming arrows on the poisonous tree sap. Octavia warns them at the very last second, and two of the Skaikru attackers, Zoe Monroe and Lacroix, choke to death. Hannah declares Octavia a traitor. Meanwhile, Octavia is once again captured by Semet and his villagers, who plan on framing Arkadia for the attack.
In Polis, the Grounders prepare to execute Emerson. Lexa gives Clarke the dagger, saying vengeance is hers until Clarke changes her mind. Emerson is spared, enraging both Titus and Emerson—Titus believes in "jus drein jus daun," and Emerson wants to be freed of his pain. Lexa gives a speech about their soon-prevailing legacy of peace banishes Emerson. He will live, but will be haunted by the fact that he is the last Mountain Man. Knowing this is worse than death, Clarke tells Emerson, "May you live forever."
Raven says that she has not found the second A.I. anywhere on the Ark. The A.L.I.E 2.0 was not on any of the twelve stations, although it is confirmed that Becca went into space with it. Jaha explains that there was a thirteenth station, the one that was blown out of the sky in an effort to convince/force the other twelve to join the Ark. It was called "Polaris." Titus is revealed to have captured John Murphy and is torturing him, interrogating him with questions about Clarke until he turns his focus onto the key to the City of Light, which he had found on him. He begins to flog Murphy again when he doesn't answer Titus's questions, and the camera pans away to a pod over to the side, which reads "Pol**is, the "a" and "r" having been singed away from the craft to read "Polis."