Season synopsis
Contains spoilers for this season and earlier seasons.
After their long journey from Earth, the survivors explore Alpha, a moon with breathable air and a settlement called Sanctum. A red-sun eclipse sends the newcomers into violent hallucinations, and the group discovers that the apparently orderly community is ruled by the Primes, people who use mind drives to transfer their stored consciousness into new Nightblood hosts. Each resurrection preserves a Prime by erasing the person whose body is taken, turning Sanctum’s ceremonies into a system of hidden killings.
Josephine Lightbourne takes Clarke’s body, but Clarke remains alive inside her own mind. Bellamy and the others search for a way to bring her back, while Clarke fights Josephine inside her mind and regains control with Bellamy’s help. The growing rebellion exposes the Primes’ use of hosts and pits Sanctum’s residents against their supposed gods. In the finale, Clarke’s deception is exposed; she ejects Simone, who has taken Abby’s body, and her guards through an airlock, while Madi struggles against Sheidheda, the former Commander whose presence in the Flame has begun to control her.
Raven deletes the Flame to free Madi, though Sheidheda’s consciousness escapes to an unknown place. The fight for Sanctum ends with the survivors confronting the Anomaly, whose mystery has been building around Octavia, Diyoza and Gabriel. Gabriel recognizes symbols on Octavia’s back as a code; when Gabriel enters it at the Anomaly Stone, the green phenomenon surges. Diyoza’s now-adult daughter Hope appears, says someone still has her mother, stabs Octavia, and collapses. Octavia vanishes in the Anomaly’s smoke, leaving her fate unresolved at the season’s end.