Season 2, Episode 16
Blood Must Have Blood Part 2
Clarke joins Octavia in the tunnels and Octavia shows her Fox's mutilated corpse from bone marrow extraction, and is let into Mount Weather by Bellamy. With the 47 waiting for bone marrow extraction, Clarke and Bellamy take Dante hostage. When Cage still refuses to stop, Clarke shoots his father, which leads Cage to begin bone marrow extraction on Abby. Seeing no other option, Clarke has Monty hack into Mount Weather's air filtration system and she and Bellamy irradiate the mountain, eradicating the population, including Maya. Cage escapes but comes upon Lincoln who injects Cage with the reaper drug, killing him, leaving Emerson, who also escaped, as the last mountain man. Everyone returns to Camp Jaha, but Clarke, wracked with guilt, leaves. Meanwhile, Jaha and Murphy arrive at an island where they separate. Murphy finds a lighthouse inside of which he watches a recording of the previous occupant who says that "she got the launch codes", before shooting himself. Jaha finds a well kept mansion, surrounded by drones, where he meets an A.I., named "A.L.I.E.", who thanks him for his "gift": the nuclear warhead from the missile he used to land on Earth.
- A.I. Is a Crapshoot: A.L.I.E. is introduced and it is revealed that she started the nuclear apocalypse and has an ambiguous plan that may affect everybody.
- Bookends: In The 48, Clarke was faced with the choice of pulling a lever in Mount Weather, knowing that if she did it would kill all the Mountain Men inside. She chose not to there. Here, she and Bellamy pull it together and kill them all.
- Downer Ending: The episode ends with Clarke and Bellamy flooding Mount Weather with radiation killing all of the Mountain Men including Maya who dies in Jasper's arms. Clarke can't bring herself to join the Sky People and leaves. Meanwhile Jaha finds the AI that started the nuclear war and learns that he she is in possession of the nuclear warhead he rode to the ground with.
- Also doubles as a Bittersweet Ending because Clarke was able to get her people out of Mount Weather because of her decision.
- Empathy Doll Shot: A soccer ball that several of the Mountain children were playing with, is shown after Clarke irradiates the Mountain.
- Genocide Dilemma: Clarke has to decide whether to irradiate all of Mount Weather that will kill all the residents even the children and the innocent or let the Mountain Men kill some of her people including her mother and her friends in their attempt to extract Bone Marrow to cure their people. She chooses to irradiate Mount Weather.
- Ironic Echo: "I bear it, so they don't have to." Said by Dante to Clarke, then later Clarke to Bellamy.
- Karmic Death: Cage is killed by Lincoln who he tortured into being a Reaper. Lincoln even uses the Reaper Drug to kill him.
- Not So Different: It is implied that Clarke realized this about herself and Dante when she made the decision to pull the switch as they both crossed a line to save their people and later repeats his statement "I bear it so they don't have to" to Bellamy.
- Pet the Dog: Indra gives Lincoln the choice to go back and help out the Sky People.
- Sacrificial Lamb: Fox's death via bone marrow harvesting at the very beginning, it was even shown as the preview for the episode. Being a background delinquent, she was likely to die eventually, but as she had a name and had been in the show since the beginning, her death was meant to be marginally sadder than the average red shirt delinquent. Her death was used to inspire a sense of urgency, as it showed the Mountain Men were quickly killing off the delinquents.
- Wham Episode: All the Mountain Men are dead at the end and Clarke leaves to parts unknown and it is revealed that an artificial intelligence is responsible for the nuclear strike that destroyed the Earth and that she has a nuclear warhead and wants Jaha to help her use it for something.