After discovering a horrifying project in Mount Weather's medical ward, Clarke joins forces with an unexpected ally.

Clarke is faced with a difficult choice and Raven helps Bellamy navigate Mount Weather as Dr. Tsing begins to harvest the 47, while Jaha and Murphy encounter a stranger on their journey to the City of Light.

Wick and Raven are faced with a setback. Maya and Jasper witness a terrible act.

Bellamy and Kane risk life and limb to rescue Clarke. In an attempt to avoid worrying about her daughter, Abby focuses on whether to open Mount Weather as a medical facility. Meanwhile, Murphy plots to betray his former Chancellor.

Clarke finds hope in the most unlikely place. Meanwhile, Alie’s master plan comes together.

Octavia fights in the final battle for her people's survival, but not everyone is willing to play fair.

Jaha and Kane disagree over how to handle their grim reality. Meanwhile, Clarke leads a group to save a friend.

Bellamy leads the charge investigating a potential way home. Meanwhile, Clarke and Madi deal with the new, uncertain threat to their home.