After the surviving 100 attempts to escape from their camp, they are ambushed in the forest by Grounder scouts and forced to hunker down in their fortified camp. Bellamy wants to stay place and fight the Grounders when they attack despite the continuing protests of Clarke who still believes that they should try to make a run for the Atlantic Ocean. Meanwhile, the remaining 1,000 citizens of the Ark prepare to return to Earth. However, the explosives that are required to remove the rest of the Ark from the Earth Monitoring Station have not worked properly and someone must remain behind to activate them manually. Kane volunteers, however, before he can get to Earth Monitoring, Chancellor Jaha has beaten him there, abandoning himself on the Ark with about one to two weeks of oxygen left. Abby and Kane, as well as the rest of Mecha station, safely make it to the ground. Back at the 100's fortified camp, Tristan leads the Grounders to attack the camp. Finn and Lincoln show up after leading a group of Reapers into the carnage, leading to a three-way war between the cannibal Reapers, Grounders, and the surviving 60 to 70 teens of the original 100. Lincoln manages to carry the wounded Octavia away from the battle area. Jasper manages to activate the dropships' fuel-cell rockets, killing Tristan as well as all the Grounders and wounded teens outside the dropship in a massive explosion (including apparently Finn and Bellamy). Anya is captured when she attempts to stop the surviving 100 from activating the rockets. After the battle's end, yet another enemy appears whom are the "Mountain Men"; heavily armed soldiers in military uniforms, gas masks and automatic weapons. The soldiers throw in a sedative gas and capture everyone. In the final scene, Clarke wakes up in a bright white hospital room. She sees Monty in the next room across the hallway and a sign next to his door that says "Mount Weather Quarantine Ward".