Nearly a century after a nuclear apocalypse, the survivors aborad a space station face a dilemma when their support systems begin failing. Their only hope of survival lies in their return to Earth, so they send 100 delinquents to brave the terrain of a ravaged planet to determine if Earth is...Read more habitable.
As Clarke discovers a new survivor population that went underground to survive, she learns a horrifying secret about what they do to other survivors. The conflict continues between the different survivor communities and the Ark survivors, sparking a series of bloody clashes.
With Clarke retreating into the woods on her own, the rest learn that there is a bounty on her head. Lexa reveals her plans to built a larger coalition, which embroils her in conflict.
With an impending nuclear disaster on the horizon, everyone tries to figure out a way to survive a catastrophe that could spell the end of humanity once and for all.
After surviving the death wave, Clarke tries to navigate a desolate Earth as Octavia takes control of the space ship and its survivors. Bellamy fights to find a way back to Earth.
As a small group tries to explore the moon Alpha, many of the Wonkru team on the Mothership must deal with the ramifications of their decisions.
As the different factions settle down in Sanctum, the Anomaly proves to be a mysterious force that both complicates things and offers a way to salvation.