Bellamy must venture into enemy territory with an unlikely companion. Meanwhile, Octavia is forced to confront her past.

Russell seeks justice. Meanwhile, Gabriel must make a difficult choice. Lastly, the Blake siblings reunite.

Bellamy and Octavia must work together to save their friends. Echo is forced to face her past.

A special Naming Day changes everything in Sanctum. Gabriel comes face to face with an old friend.

Sanctum becomes a battleground between the devout and the non-believers. The mystery of the anomaly deepens.