Plot summary
After the first test kills the thief, Emori's lie is discovered and she is taken prisoner, with the intention of using her as the next subject. Murphy also has to be tied up when he tries to stop them, and Luna is knocked out by Roan when she tries to leave. Clarke changes her mind and injects herself with Luna's bone marrow, becoming a Nightblood, but before she can subject herself to the radiation, Abby destroys the machine, with her hallucinations having convinced her that Clarke would die. In Arkadia, Jaha overhears Niylah use a phrase associated with the cult who built the shelter, and believes that the shelter he found was a decoy.
Suspecting Gaia may have information that could lead to the real shelter, he, Kane and Monty go to Polis, where the Tree People are fighting the Ice Nation for control. Gaia helps them deduce that the shelter is beneath Polis, and they find it using a talisman found at the decoy shelter.
Credits
Adapted from Wikipedia contributors, List of The 100 episodes. HTML formatting and reference markers removed.