After arriving in orbit of a brand new world, the survivors from Earth send an expedition to the surface. Back on the ship, Abby and others from Wonkru face the consequences of their choices.
Clarke and the others discover the reason why the Alpha settlement is abandoned, and must lock themselves up in order to avoid killing each other -- unable to warn the ship in orbit that a group of potential hostiles is headed toward them. Raven wakes an ally in the hopes of retaking the ship.
When the inhabitants of Santum return home Clarke makes an appeal to their leader, Russell, for them to stay. Bellamy, Echo, and Octavia are sent to retrieve the transport ship, and discover a dangerous new faction in the woods.
As Delilah's Naming Day arrives Clarke embraces the colony's traditions, seeking to make amends with her friends. Outside the shield Diyoza is recruited to help rescue Rose, and a traitor inside Sanctum is revealed.
Josephine takes her new body out on a mission to learn whether there are any more Nightbloods among the newcomers from Earth. Bellamy, Jordan, and the others learn the unsettling truth about the Primes, while Octavia and Diyoza fight to survive in the wilderness.
While Bellamy plots revenge against the Primes, Murphy tries to help Josephine get her way. Octavia suffers from her exposure to temporal radiation, and Maddie is tormented by visions of the Dark Commander.
Clarke awakens as a prisoner inside her own mindspace, where she moves through her history in a fight with Josephine over a secret -- and for final control of her body.
While Diyoza and Octavia follow their companion into the mysterious temporal anomaly, Maddie tries to convince the others to take Sanctum by force. Abby attempts to create a new Nightblood for the Primes, and Josie seeks help to eliminate Clarke once and for all.
An encounter with the anomaly forces Octavia to reckon with her past, leading to a confrontation with Blodreina herself. Bellamy takes Josephine into enemy territory, while Kane must decide whether the price of his new life is too high to pay.
While Russell plans to execute one of Wonkru in retribution for Maddie's crime, Echo works with Ryker to disrupt the execution. Meanwhile, Josephine and Clarke fight to stay alive -- both inside and outside their shared mindspace.
Clarke and Bellamy must convince the Children of Gabriel to along with their plan to attack Sanctum. As Maddie continues to tangle with the Dark Commander, Echo is subject to the Nightblood experiment, and reveals her dark past to Ryker.
Clarke poses as Josephine to get close to Russell, who is forcing Abby and the others to create Nightbloods to save his wife and bring back the glory of the Primes. With an attack on Sanctum imminent, Gabriel takes matters into his own hands.
The Primes storm the ship in orbit, with a plan to leave orbit -- and wipe the minds of everyone in stasis. Meanwhile with Sanctum in turmoil Murphy and Emori attempt to intervene before mass slaughter, and the Dark Commander takes control of Maddie.
